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The electronic structures and optical properties of intrinsic GaSb and GaSb doped with rare earth elements Sc and Tm were studied by first principle calculation method based on the density functional theory (DFT). The calculation results show that the Sc and Tm doped GaSb materials are direct band gap P-type semiconductors. The Sc-doped GaSb material induces a shallow energy level defect state in the conduction band and the band gap becomes narrower. Tm doping induces deep energy level defect states in the conduction band and the band gap becomes wider. Sc and Tm doping reduces the energy loss and enhances the absorption of GaSb photons in the mid-infrared band. Among them, the Sc doping is more effective, where there is an absorption peak at 4.3 μm (0.28 eV) with the peak value of 1.7 × 10~5 cm-1, and the light absorption coefficient still reaches 1 × 10~5 cm-1 until the wavelength is 6.8 μm (0.18 eV). The results provide a theoretical reference for expanding the application of GaSb-based semiconductor materials in infrared detectors and infrared semiconductor lasers. [ABSTRACT FROM AUTHOR]

The surface quality of the substrate has an important effect on the quality of the growth film. The roughness, uniformity, adhesion residue and oxide layer of the substrate are the evaluation criteria of its surface performance. In this paper, an in-situ thermal treatment method to remove the natural oxides on GaSb (001) substrates for epitaxial growth of CdZnTe films by close-spaced sublimation method was reported. By controlling the temperature and time of the thermal treatment, a clean and smooth substrate state is obtained. The effect of thermal treatment on the morphology and composition of GaSb substrate was analyzed by atomic force microscopy and X-ray photoelectron spectroscopy. The crystal quality of CdZnTe epitaxial film grown on GaSb substrate after thermal treatment was evaluated by double crystal X-ray curve. In order to further study the properties and epitaxial formation mechanism of the micro-defects near the heterogeneous interface, TEM analysis of CdZnTe/GaSb cross section was also carried out. After 180 s thermal treatment at 600 ℃, the GaSb substrate can obtain a clean and relatively flat surface after most of the oxide is removed from the substrate surface, thus improving the crystallization quality of CdZnTe epitaxial film. The full width of half maximum of double crystal X-ray curve is 94″, which approached the crystalline quality of bulk CdZnTe crystal ever reported. [ABSTRACT FROM AUTHOR]

Gallium antimonide (GaSb) is a III-V semiconductor of technological interest for low-power, high-mobility field-effect transistors, as well as for mid-wave infrared detectors. In such devices, GaSb interfaces with other III–V semiconductors with different lattice constants that can induce strain in the GaSb layers. Two dominant limiting factors in hot carrier relaxation are the intra-valley and the inter-valley electron–phonon (e-ph) scattering. In GaSb, these are sensitive to the Γ –L energy ordering, which depend intimately on the strain. Here, we report ab initio calculations of electronic structure, phonon dispersion, e-ph scattering and relaxation times for GaSb as a function of strain. As observed previously for other group IV and III-V semiconductors, our results show strong anisotropy, a strong contribution from LO phonons, and the need to go beyond the deformation potential scattering. For GaSb, the main finding is that a compressive strain between 0.4% and 0.6% converts GaSb from a direct-bandgap semiconductor to an indirect-bandgap semiconductor, with dramatic changes in the competing scattering rates and carrier relaxation times. [ABSTRACT FROM AUTHOR]

A triple-metal-gate stacked III–V vertical tunnel field-effect transistor (TM-GS-VTFET) structure is examined. There are two different TM-GS-VTFETs: Device-A, which uses a source pocket, and Device-B, which uses a new source extension approach. Source pocket-engaged TFETs are recognized for their enhanced ON-state current (ION) and subthreshold swing compared to traditional TFETs. However, they may require more complex fabrication procedures. The source extension strategy alters the electric-field distribution and decreases the tunneling barrier width near the source side. This boosts the tunneling rate and increases the device functioning. The simulation was performed using the Silvaco Technology Computer-Aided Design (TCAD) tool. Various analog and radio-frequency (RF) parameters were examined. The ION in Device-B was found to be $234.03~\mu \text{A}/\mu \text{m}$ , the OFF-state current (IOFF) was $1.52\times 10^{\mathrm {-14}}\text{A}/\mu \text{m}$ , Sub-threshold swing (SS) was 28.58 mV/decade, and the transconductance (gm) was $245.28~\mu \text{S}/\mu \text{m}$ . The RF frequency parameter such as cutoff frequency (fT), oscillating frequency (fmax), and Gain Bandwidth Product (GBP) were 152.45 GHz, 830 GHz and 25.16 GHz respectively. It was observed that Device-B exhibited 11 times higher ION, 3.2 times higher GBP, and 3.15 times higher fmax than Device-A. The utilization of this source extension technique has proven to be advantageous for achieving enhanced analog and RF properties in TFETs.

In recent years, antimonide infrared technology has developed rapidly and has become one of the important development directions of semiconductor technology. Gallium antimonide (GaSb), as a typical III-V compound semiconductor, has become a key substrate material for antimonide infrared optoelectronics due to its excellent properties. The demand for GaSb wafers is increasing, and higher requirements are also put forward with the maturing and application of antimonide infrared technology. The properties of epitaxial materials and devices are directly affected by substrate quality, so that GaSb substrates are required to have the characteristics of large size, lower defect density, better surface quality and consistency. The properties, growth methods, research progress at home and abroad, as well as applications of GaSb crystal are reviewed in this paper, and the development prospects are also analyzed. [ABSTRACT FROM AUTHOR]

Owing to the narrow bandgap and excellent optoelectronic properties, III‐Sb nanowires (NWs) enable efficient optical response from near‐infrared to mid‐infrared, making them ideal candidates for broadband optical modulation. Herein, high‐purity GaSb NWs with controlled density are prepared on the transparent substrates of glasses. The phase purity and crystallinity of as‐prepared GaSb NWs are verified by X‐ray diffraction. Z‐scan and I‐scan techniques are adopted to investigate the nonlinear optical modulation properties, displaying a high modulation depth of 40% (at 1 μm wavelength) for the GaSb NWs with growth time of 30 min. Furthermore, the as‐prepared GaSb NWs are used as the saturable absorber elements in a waveguide laser cavity, demonstrating efficient Q‐switched mode‐locked lasers with a repetition rate of 8.2 GHz and a pulse duration of 31 ps (operating at 1 μm wavelength). All results show the great potential of GaSb NWs for the ultrafast laser and nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Owing to the narrow bandgap and excellent optoelectronic properties, III‐Sb nanowires (NWs) enable efficient optical response from near‐infrared to mid‐infrared, making them ideal candidates for broadband optical modulation. Herein, high‐purity GaSb NWs with controlled density are prepared on the transparent substrates of glasses. The phase purity and crystallinity of as‐prepared GaSb NWs are verified by X‐ray diffraction. Z‐scan and I‐scan techniques are adopted to investigate the nonlinear optical modulation properties, displaying a high modulation depth of 40% (at 1 μm wavelength) for the GaSb NWs with growth time of 30 min. Furthermore, the as‐prepared GaSb NWs are used as the saturable absorber elements in a waveguide laser cavity, demonstrating efficient Q‐switched mode‐locked lasers with a repetition rate of 8.2 GHz and a pulse duration of 31 ps (operating at 1 μm wavelength). All results show the great potential of GaSb NWs for the ultrafast laser and nonlinear optical applications.

The gallium antimonide (GaSb) material has very attractive electronic and optoelectronic properties which are suitable for next‐generation infrared (IR) photodetector applications. In this work, properties of undoped GaSb material such as density of states, bandstructure, electron density, absorption coefficient, dielectric function, refractive index, and extinction coefficient are calculated using density‐functional theory (DFT). Moreover, the effects of doping with Ge, Sn, and Zn elements on these properties of GaSb material are investigated. It is found that undoped GaSb material exhibits a direct gap of ≈0.72 eV. Among different doping elements, Ge‐doped GaSb produces a very significant enhancement in optical properties. The Ge‐doped GaSb demonstrates a four times higher absorption coefficient in comparison to undoped GaSb in the IR region at 0.8 eV photon energy. GaSb‐based photodetector device is designed using the Solar Cell Capacitance Simulator (SCAPS) 1D tool. The efficiency of the designed photodetector with optimum thicknesses and doping of different layers is found to be improved from 21.34% to 25.91% after incorporating the absorption data set obtained from the DFT calculations. Additionally, the photodetector with optimum parameters demonstrates maximum responsivity of value ≈0.31 A W−1. In the previous findings, it is demonstrated that GaSb is a very suitable material for next‐generation IR photodetector applications. [ABSTRACT FROM AUTHOR]

Optical absorption spectra of GaSb/GaAs quantum-ring-with-dot structures (QRDSs) are calculated using Fermi's golden rule by which the electronic states involved in the optical transitions are obtained from the eight-band k ⋅ p method. The absorption spectra of multi-stacked QRDS layers show that the interband and intraband transitions are favorable to intermediate band solar cells (IBSCs). A drift-diffusion model with rate equations for a solar cell containing multi-stacked QRDS layers is formulated based on the absorption spectra. The external quantum efficiency (EQE) determined by the model with the AM1.5 solar spectrum and additional infrared light demonstrates that the confined hole states in the quantum ring (QR) parts of the QRDSs effectively function as an IB. The more efficient two-step photon absorption indicated by the enhancement of the EQE also suggests the potential of QRDSs for the IBSCs. [ABSTRACT FROM AUTHOR]

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Ion implantation induced damage in GaSb and its removal by rapid thermal annealing (RTA) have been investigated by Raman spectroscopy. The evolution of the Raman modes as a function of implantation fluence, annealing temperature and time has been analyzed. Results indicate that a lattice quality that is close to as-grown GaSb has been obtained by annealing the implanted samples at 500 °C for 45 s. However, consequent surface analyses by scanning electron microscope (SEM) and atomic force microscope (AFM) show that a heavily perturbed layer contains voids due to the outdiffusion of Sb atoms on the surface remains. Mechanism of the damage recovery and the structure of the implanted layer are discussed based on the experimental results. [ABSTRACT FROM AUTHOR]

Photonic integrated circuits fabricated using a Si3N4 waveguide platform exhibit low losses in a wide wavelength region extending from visible to beyond 2 µm. This feature is exploited to demonstrate a high‐performance integrated laser exhibiting broad wavelength tuneability near a 2.6 µm wavelength region. The laser is based on a Si3N4 photonic integrated circuit incorporating a tunable reflector and a AlGaInAsSb/GaSb quantum‐well gain element. A tuning range of 170 nm (2474–2644 nm) and single‐mode CW operation with a maximum power of 6.4 mW at room temperature are demonstrated. The performance is enabled by exploitation of several essential building blocks realized in Si3N4, namely low‐loss Y‐branches, inverse tapers, and a double‐ring resonator with a free spectral range of ≈160 nm. Moreover, the limits of wavelength coverage are explored using Si3N4 waveguides and show that the platform supports low propagation loss up to 3.5 µm. Finally, the possibility to achieve improved mode matching between Si3N4 and GaSb waveguides is analyzed, further enabling enhancing the performance of such a hybrid laser platform and supporting wavelength extension beyond a 3 µm range. [ABSTRACT FROM AUTHOR]

Wide band gap semiconductor nanomaterials have great research prospects in power semiconductor devices, radio frequency devices, optoelectronic sensor devices, and so on. Among them, gallium oxide is considered as the representative material of wide band gap semiconductor nanomaterials as a deep ultraviolet (UV) photoelectric sensing device because of its 4.9 eV band gap width. However, the traditional synthesis of this kind of metal oxide semiconductor nanomaterials by the chemical vapor deposition (CVD) method still has some problems. The experimental process is not easy to achieve due to the high temperature of 960 °C, and the lower photocurrent makes it difficult to read the photoelectric signal for subsequent devices because of the optical response current of the order of nanoampere. In this work, gallium antimonide and indium antimonide were selected as the nutrition reaction materials, while oxygen is used as the oxide materials. InGaO3 nanowire network materials were prepared at a lower temperature of 700 °C and a lower working pressure of 0.2 kPa, the deep UV photoelectric response of the optoelectronic devices was measured, and high performance was obtained at 5 V bias, like at a power of 0.64 μW/cm2, the response is 80.1 A/W, detection is 1.03 × 1014, and the external quantum efficiency is 3.9 × 104. Especially, the photoelectric current 34.1 μA is far larger than that of the level of several nanoampere traditional gallium oxide devices. Its reaction principle is that In and Ga metal nucleate and oxidize on the substrate to form InGaO3 nanowires after antimonide decomposition at 700 °C temperature, which is lower than 960 °C of the traditional CVD reaction method. This mechanism is different from that of traditional graphite and oxide powder reduction, which can save energy. In a word, this research has invented a method for preparing indium doping gallium oxide nanomaterials, which provides a reference for rapid preparation of response materials and low-energy consumption for deep UV photoelectric devices. [ABSTRACT FROM AUTHOR]

We present a mode−locked GaSb−based optically pumped semiconductor disk laser operating at 2 µm based on the self−mode−locked mechanism. Using the delay differential equation model, we discuss the influence of cavity length on the stability of self−mode−locking and design a Z−shaped long cavity for self−mode−locking. Employing an aperture and an F−P etalon in the cavity length of ~365 mm, we obtain stable self−mode−locking at a center wavelength of 2034.5 nm, with a pulse duration of 255.48 ps and average output power of 173 mW at a repetition rate of 404 MHz. [ABSTRACT FROM AUTHOR]

GaSb-based interband cascade lasers (ICLs) emitting at a center wavelength of 6.12 µm at 20 °C in continuous-wave operation up to a maximum operating temperature of 40 °C are presented. Pulsed measurements based on broad area devices show improved performance by applying the recently published approach of adjusting the Ga1-xInxSb layer thickness in the active region to reduce the valence intersubband absorption. The W-quantum well design adjustment and the optimization of the electron injector, to rebalance the electron and hole concentrations in the active quantum wells, improved the device performance, yielding room temperature current densities as low as 0.5 kA cm-2 for broad area devices under pulsed operation. As a direct result of this improvement together with optimizations of the waveguide design, the long wavelength limit for GaSb-based ICLs in continuous-wave operation could be extended. For an epi-side down mounted 23 µm wide and 2 mm long device with nine active stages and high-reflectivity back facet, the threshold power is below 1 W and the optical output power is over 25 mW at 20 °C in continuous-wave mode. Such low-threshold and low-power consumption ICLs are especially attractive for mobile and compact sensing systems. [ABSTRACT FROM AUTHOR]

In this study, the analog and radio frequency (RF) functionality of an indium arsenide-gallium antimonide (InAs-GaSb) tunnel field-effect transistor (TFET) with an InAs pocket layer is examined. The potential advantages and disadvantages of TFETs in comparison to their traditional counterparts are thoroughly analyzed. The conductivity of the channel is modulated by an InAs pocket layer. The InAs-GaSb vertical TFET (VTFET) with an InAs pocket layer (device B) yields higher ON-current (6.39 × 10−6 A/μm) compared to the InAs-GaSb VTFET (device A) (5.18 × 10−8 A/μm). Additionally, device B offers low OFF-current (2.26 × 10−17 A/μm) compared with device A (1.14 × 10−16 A/μm). The channel resistance values are 2 × 10−5 Ω·cm for device B and 5 × 10−3 Ω·cm for device A. The transconductance (gm) values for device B and device-A are 0.78 mS/μm and 0.37 mS/μm, respectively. Device B has a cutoff frequency (fT) of 37 GHz whereas that for device A is only 22 GHz at VGS = 0.6 V. Compared to standard TFETs, the fT of the proposed design is 15 GHz higher owing to increased transconductance. The ON-state loss can be reduced by lowering the channel resistance. The InAs pocket layer in InAs-GaSb VTFETs makes them ideal candidates for low-power RF and analog applications. [ABSTRACT FROM AUTHOR]

issues related to the thermal stability of front contacts, based on Cr–Au and Cr–Au–Ag–Au, to GaSb-based photovoltaic cells have been considered at the operational (the cell temperature is 50°C) and standard conditions as well as at the forced thermal degradation (at 125 and 200°C). It is shown that the photovoltaic converter with the silver-containing contact is preferable in terms of the stability of contact resistivity, external quantum yield, FF, Voc, and therefore, the cell efficiency and service life. The durability of the cells is determined at operational and elevated temperatures. [ABSTRACT FROM AUTHOR]

Type-II superlattices (T2SLs) are emerging as next-generation materials for infrared detectors. The epitaxial quality of T2SLs is of great importance to the performance of infrared detectors such as dark current and detectivity. Herein, we explore the effect of the native GaSb oxide layer on the surface morphology and crystal quality of InAs/GaSb T2SLs grown with molecular beam epitaxy. The experimental results demonstrate that the thickness of the oxidation layer on GaSb substrates gradually increases over time and is saturated at around 73 Å in the natural oxidation condition. Moreover, the oxidation process is sensitive to humidity. As the thickness of the GaSb oxide layer increases from 18.79 Å to 61.54 Å, the full width at half maximum of the first satellite peak increases from 38.44 to 61.34 arcsec in X-ray diffraction measurements, and the root mean square roughness increases from 0.116 nm to 0.171 nm in atomic force microscopy measurements. Our results suggest that the thickness of the GaSb oxide layer should be less than 55 Å to obtain smooth buffer layers and qualified superlattices. The work provides an optimized direction for achieving high-quality superlattices for infrared optoelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A thermal evaporation method is used to grow GaSb NWs using Ag catalyst particles. • GaSb grown on a Si surface consists of nanowires and islands of different sizes. • Mostly nanowires are grown on nanolaminate transparent TiO 2 /Ag/TiO 2 structure. • Raman spectra reveal narrow GaSb- LO and TO lines at 235 and 225 cm−1, respectively. This paper presents a comparative study of GaSb nanowire (NWs) growth on a Si substrate using Ag nanoparticles as catalyst and on a Si substrate coated with a transparent conductive TiO 2 /Ag/TiO 2 laminate structure. Silver nanoparticles with different sizes between 30 and 70 nm were formed directly on Si surface or embedded between two TiO 2 layers by RF magnetron sputtering. A thermal evaporation method was used to grow GaSb NWs via vapor–liquid-solid (VLS) mechanism. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the surface morphology of the grown structures. Two kinds of nanostructures were observed on the surface of the Ag/Si substrate: nanowires and nanoislands of different sizes and random position, while mostly nanowires were visible for GaSb grown on TiO 2 /Ag/TiO 2 /Si substrate. Raman spectroscopy measurements were used to investigate vibrational mods and phonon confinement in the grown nanostructures. The results demonstrate that TiO 2 /Ag/TiO 2 / nanolaminate structure is a promising substrate for nanowires growth. The technology for obtaining this nanolaminate structure allows the formation of local areas with micron dimensions, using a mask as a pattern structure during the deposition of Ag nanoparticles. [ABSTRACT FROM AUTHOR]

Epitaxially-grown semiconductor quantum dots (QDs) provide an attractive platform for the development of deterministic sources of high-quality quantum states of light. Such non-classical light sources are essential for quantum information processing and quantum communication. QDs emitting in the telecom wavelengths are especially important for ensuring compatibility with optical fiber systems required to implement quantum communication networks. To this end, GaSb QDs fabricated by filling local-droplet etched nanoholes are emerging as a viable approach, yet the electronic properties of such nanostructures have not been studied in detail. In this article, an insight into the electronic structure and carrier dynamics in GaSb/AlGaSb QDs is provided through a systematic experimental analysis of their temperature-dependent photoluminescence behavior. A steady-state rate equation model is used to reveal the relevant energy barriers for thermally activated carrier capture and escape processes. Furthermore, results of detailed theoretical simulations of quantum-confined energy states using the multi-band k · p model and the effective mass method are presented. The purpose of the simulations is to reveal the direct and indirect energy states, carrier wavefunctions, and allowed optical transitions for GaSb QDs with different physical dimensions.

The authors report two approaches, the first based on growth of lattice matched InGaAs/GaAsSb superlattice on InP substrate with tunable bandgap in the 2 to 3 µm range. The second approach is based on bulk random alloy InGaAsSb, which is tunable from 1.7 µm to 4.5 µm and lattice matched to the GaSb lattice constant. In each case, detector structures were fabricated and characterised. The authors have assessed the performance of these materials relative to commercially available extended short wave infrared devices through comparison to IGA-Rule 17 dark current performance level. A complementary barrier structure used in the InGaAsSb design showed improved quantum efficiency. The materials compare favourably to commercial technology and present additional options to address the challenging extended short wave infrared spectral band. [ABSTRACT FROM AUTHOR]

We present a mode−locked GaSb−based optically pumped semiconductor disk laser operating at 2 µm based on the self−mode−locked mechanism. Using the delay differential equation model, we discuss the influence of cavity length on the stability of self−mode−locking and design a Z−shaped long cavity for self−mode−locking. Employing an aperture and an F−P etalon in the cavity length of ~365 mm, we obtain stable self−mode−locking at a center wavelength of 2034.5 nm, with a pulse duration of 255.48 ps and average output power of 173 mW at a repetition rate of 404 MHz.

The dislocation etch pit density (EPD) of the 2-inch diameter n-type (100) Te-GaSb single crystal grown in batches by the liquid encapsulated Czochralski (LEC) method is usually lower than 300 cm-2, reaching dislocation-free level. In this paper, the lattice perfection and subsurface damage of this GaSb single crystal polished substrate were characterized by X-ray rocking curve and reciprocal space map (RSM). The results show that after chemical mechanical polishing with optimized process conditions, the surface of GaSb single crystal substrate is atomically smooth, and there is no subsurface damaged layer. High-quality type-II superlattice epitaxial materials can be stably grown on this substrate by molecular beam epitaxy and exhibit excellent infrared detection performance. On this basis, the internal relationship between the physical properties, growth preparation and substrate processing conditions of GaSb substrate materials was comprehensively analyzed. [ABSTRACT FROM AUTHOR]

In this letter, we report the realization of sub-10-nm diameter vertical nanowire (VNW) p-type tunnel FETs (TFETs). Using a broken-band GaSb/InAsSb heterostructure design and a top-down fabrication approach, we demonstrate a 9-nm diameter VNW TFET with excellent on-state characteristics featuring a peak transconductance of 90 $\mu \text{S}/\mu \text{m}$ at $V_{{\text {ds}}} = -0.3$ V. The same device exhibits a minimum linear subthreshold swing of 225 mV/dec at $V_{\text {ds}} = -0.05$ V. Our p-type GaSb/InAsSb TFETs exhibit clear negative differential resistance at room temperature, with a peak-to-valley current ratio over 3. The excellent device performance of these devices bodes well for the viability of GaSb-based complementary TFETs in future ultra-scaled logic technologies. [ABSTRACT FROM AUTHOR]

Financial disclosure is crucial to achieve fiscal transparency and government accountability. In 2004, the Governmental Accounting Standards Board (GASB) issued Statement No. 45 to require the disclosure of information about other postemployment benefits (OPEB). Using a panel of U.S. counties and the bonds they issued between 1999 and 2012, this paper examines the effects of GASB 45 on municipal borrowing costs. GASB 45 increases borrowing costs of county governments, with the effects decreasing over time. GASB 45 has a larger effect on borrowing costs of county governments issuing bonds of lower credit quality and adopting the generally accepted accounting standards (GAAP). [ABSTRACT FROM AUTHOR]

The interfacial InAs layers can improve the metal-oxide-semiconductor (MOS) interface properties of n-type GaSb (n-GaSb) MOS capacitors (MOSCAPs) with Al2O3 insulating layers deposited by an ex situ atomic-layer deposition (ALD) process. The n-GaSb MOSCAPs show the capacitance response in the accumulation region at RT, but they did not show the response with any low frequency at 100 K, indicating the quite high interface trap density (D it). On the contrary, the n-GaSb MOSCAPs with the interfacial InAs layers show sufficient accumulation responses at 100 K as well as RT, indicating the lower D it. The 1.5 nm thick InAs/n-GaSb MOSCAP with ALD-Al2O3 deposited at 150 °C exhibited relatively low D it of 2.6 × 1013 cmâˆ'2 eVâˆ'1, and the 2.5 nm thick InAs/n-GaSb MOSCAP with ALD-Al2O3 deposited at 300 °C exhibited low D it of 2.6 × 1012 cmâˆ'2 eVâˆ'1, while the 2.5 nm thick InAs layers can induce the delay of the response of electrons with the high frequency measurements at low temperature. [ABSTRACT FROM AUTHOR]

هیئت استانداردهای حسابداری دولتی، استانداردهایی را در جهت گزارشگری مالی دولت‌های محلی و ایالتی وضع میکند. این استانداردها در جهات مختلف، راهنمایی برای دولت‌ها است تا با استفاده از آن، امور و گزارشگری مالی خود را بهتر و کاراتر انجام دهند. با توجه به محیط پویا و دائماً در حال تغییر بخش دولتی، و همچنین با توجه به مباحث جدیدی که همواره در موضوعات مالی دولتی (ازجمله در حسابداری بازنشستگی و واحد گزارشگری مالی در سال‌های گذشته) ظهور می‌کند، هیئت مذکور باید به‌طور مستمر، استانداردهای خود را ارزیابی و بازنگری‌های لازم را انجام دهد. اعمال تغییرات مؤثر در این زمینه از سوی هیئت فوق باعث خواهد شد تا کاربران گزارشات مالی بتوانند تصمیمات آگاهانه‌تری بگیرند و همچنین دولت‌ها می‌توانند در زمینه نظارتشان بر منابع عمومی، پاسخگوی عموم باشند؛ از طرف دیگر قابلیت مقایسه‌پذیری دولت‌ها نیز فراهم خواهد شد.

اندازه‌گیری ارزش منصفانه و بکارگیری آن همواره یکی از موضوعات مهم بوده است. با انتشار استانداردهای بین‌المللی گزارشگری مالی (IFRS)، موضوع ارزش منصفانه بیشتر مورد توجه قرار گرفت. در کشور ایران نیز پذیرش IFRS نشان از توجه به رویکرد ارزش منصفانه داشته، تاجایی که اهمیت این موضوع و بررسی ابعاد آن باعث شده تا اخیراً آخرین استاندارد حسابداری کشور (استاندارد 42) به این مفهوم اختصاص یابد. در بخش دولتی اما، موضوع کمی تفاوت دارد. هئیت استانداردهای حسابداری دولتی امریکا (GASB) در سال 2015 «بیانیه شماره 72» یعنی اندازه‌گیری و کاربرد ارزش منصفانه را صادر کرد. این بیانیه برای شفاف‌سازی ابهاماتی ازجمله راهنمایی نحوه استفاده از ارزش منصفانه در صورت عدم دستیابی به ارزش‌های بازار و نیز ضرورت قضاوت‌های مدیریت طراحی شد. در مقاله حاضر به اهم موارد این بیانیه بویژه اندازه‌گیری، کاربرد و افشاء ارزش منصفانه پرداخته خواهد شد. هدف نهایی این بیانیه، بهبود سازگاری و مقایسه‌پذیری نحوه اندازه‌گیری و اِعمال ارزش منصفانه از سوی دولت‌ها و افشای اطلاعات مربوط به آن اندازه‌گیری‌ها است.

In this paper, the performance of GaAs and GaSb based sub-10 nm double-gate junctionless metal-oxide-semiconductor field-effect transistors (DG-JLMOSFETs) have been studied for high-performance switching applications. The quantum transmitting boundary method (QTBM) has been considered for electron transport, and the band structures are accounted for sp3d5s* tight-binding modeling. The channel thickness, tch is varied from 1.7 to 4.7 nm to evaluate the device figure of merits (FOMs). The thinner channel’s device shows a lower OFF-state current, while the ticker channel device allows a higher ON-state current. The threshold voltage is approximately 0.4 V for GaAs DG-JLMOSFETs with tch = 1.7 nm, whereas it reduces to ~0.05 V for that of tch = 4.7 nm. Similar characteristics have been shown in GaSb devices. Besides, a significant impact of tch on the subthreshold swing (SS) and drain-induced barrier lowering (DIBL) is found in GaSb DG-JLMOSFETs compared with those of GaAs devices. The devices show a higher leakage-power dissipation in both channel materials and low-intrinsic delay for thicker tch due to a substantial amount of energy drop. The above results indicate that III-V-based DG-JLMOSFETs are very promising for next-generation high-performance switching technology.

In this study, we demonstrated low leakage current and high mobility thin body (In)GaSb p-FETs. Through the optimization of the V/III ratio during the epitaxial growth, we achieved a highly insulating bottom Al0.95Ga0.05Sb barrier, which eliminates the junction leakage. We also suppressed the interface trap-assisted surface leakage current by introducing In0.53Ga0.47As surface passivation on the GaSb channel. Furthermore, GaSb/InGaSb/GaSb quantum well (QW) channel structure provided significant improvement in effective mobility ( ${\mu }_{\mathrm{ eff}}$ ) characteristics. As a result, the fabricated devices showed the lowest off-leakage current ( ${I} _{\mathrm{ off}}$ ), subthreshold slope ( ${S}$ . ${S}$ .) and high $\mu _{\mathrm{ eff}}$ among reported GaSb p-MOSFETs.

We have fabricated GaSb/Ge2Sb2Te5 (GST) superlattice-like structure thin films for phase change memory by magnetron sputtering method, and investigated their phase transition behavior and electrical properties. The experimental results show that increasing the thickness ratio of the GaSb layer to the GST layer can increase the crystallization temperature and reduce the threshold voltage, which is conducive to improving the thermal stability of the GaSb/GST thin films. By analyzing the differences in morphology, thickness and element distribution during phase transition, it is found that the volume of the GaSb layer decreases with the increase of annealing temperature, while the volume of the GST layer expands gradually. However, the volume change range of GaSb/GST thin films is not obvious. Controlling the volume change of the GaSb/GST thin films during phase transition can prolong the service life of the device. By observing the diffusion of interface elements in GaSb/GST superlattice films during annealing, we have found that the interface mixing of Ge element is the most obvious, and Te element have a clear trend of aggregation to adjacent GaSb layers. [ABSTRACT FROM AUTHOR]

Binary semiconductors are one of the nominee materials for the manufacture of third-generation infrared photon detectors and ICs with ultra-high speed and ultralow power consumption. In this work, we present the electronic properties of IV-IV (SiC) and III-V (GaSb, InSb) semiconductors in Zinc-blend (ZB), Rocksalt (RS), and Wurtzite (WZ) Phases and the structural Phase transition using first principle. Our result shows that SiC, GaSb and InSb crystallize as metals in the RS Phase but as semiconductors in the ZB (WZ) Phases with an energy gap of 1.30 eV (2.26 eV), 0.23 eV (0.14 eV) and 0.17 e V (0.21 eV) respectively; indicating that both GaSb and InSb are narrow bandgap semiconductors while SiC is a wide bandgap semiconductor. These results are in good agreement with other theoretical and experimental reports. A phase transition from ZB - RS and from WZ - RS phases is observed at a pressure of 9.72 GPa (7.65 GPa), 72.4 GPa (72.4 GPa) and 8.063 Gpa (8.063 Gpa) for InSb, SiC and GaSb respectively. This shows that under high pressure, the materials undergo a transition from the semiconducting (ZB or WZ) Phase to the metallic (RS) Phase. [ABSTRACT FROM AUTHOR]

We present the first modelocked backside-cooled GaSb VECSEL (Vertical External Cavity Surface Emitting Laser) operating above $2 ~\mu \text{m}$. Using a two quantum well InGaSb SESAM (SEmiconductor Saturable Absorber Mirror) in a V-shaped cavity arrangement we obtain femtosecond modelocking at a center wavelength of 2061 nm, with pulses as short as 324 fs, an average output power as high as 65 mW at a repetition rate of 3 GHz. An operation in a picosecond regime is further demonstrated with an even higher average output power of up to 260 mW and 4.5-ps pulses. We perform a characterization in both the femto- and picosecond regimes with measurements of the pulse duration, the optical spectrum, and the pulse repetition rate (frequency and time domain analysis) at low and high power. In this context, the influence of intracavity group delay dispersion (GDD) is investigated. We find that GDD has a strong influence on the pulse duration (fs or ps regime) and thus on the performance of our SESAM-modelocked 2- $\mu \text{m}$ GaSb VECSEL. [ABSTRACT FROM AUTHOR]

The issues concerning the stability of contact systems in GaSb photovoltaic converters and their reliability enhancement have been considered. It is established that at thermally induced degradation conditions (i.e., at the constant heat load at 80, 120, and 200 °C), the contacts with a conducting Ag layer, namely, Ti-Pt-Ag, Ti-Pt-Ag-Au, Cr-Au-Ag-Au have an advantage over those of conducting Au layer, i.e., Ti-Pt-Au, Cr-Au, while silver-containing metallization Ti-Pt-Ag and Ti-Pt-Ag-Au are more stable under temperature than Cr-Au-Ag-Au one. [ABSTRACT FROM AUTHOR]

گزارشگری مالی بعنوان محصول نهایی فرآیند حسابداری، تحت تأثیر ویژگی‌هایی ازجمله محیط فعالیت، نیازهای استفاده‌کنندگان و اهداف ذینفعان از اطلاعات مالی قرار دارد. اگرچه گزارشگری مالی نهادهای دولتی و عمومی و همچنین واحدهای انتفاعی و تجاری، نقش مشابهی در جهت تحقق مسئولیت پاسخگویی و فراهم نمودن اطلاعات برای تصمیم‌گیری (بر اساس تئوری مباشرت) ایفاد می‌نمایند اما گزارش‌هایی که آنها استخراج می‌کنند، تفاوت‌های قابل ملاحظه‌ای هم، با هم دارند. در عین حال گزارش‌های مالی بخش عمومی شامل عناصر و اطلاعات با اهمیت زیادی بوده و صورت‌های مالی (که برای بخش انتفاعی از بُعد قانونی تنها گزارش مالی الزامی است) فقط یکی از این اقلام بوده و از نظر سطح اهمیت نیز، پژوهش‌ها نشان داده، هم سطح با سایر عناصر گزارشگری مالی بخش عمومی می‌باشد. دولت بعنوان بزرگترین نهاد و بخش‌های عمومی، شهرداری‌ها و سایر نهادهای عمومی غیردولتی، برای تحقق اهداف خود، دو نوع فعالیت انجام می‌دهند. هیأت تدوین استانداردهای حسابداری دولتی (GASB) این فعالیت‌ها را چنین تفکیک نموده است: اول- فعالیت‌های حکمرانی (غیربازرگانی) و دوم- فعالیت‌های بازرگانی و امانی. فعالیت‌های حکمرانی (غیربازرگانی) موجب افتراق گزارشـگری مالی بخش عمومی و مؤسسات انتفاعی (خصوصی) می‌گردد؛ هرچند در اغلب کشورها، گزارشگری مالی فعالیت‌های بازرگانی و امانی بخش عمومی با مؤسسات انتفاعی بخش خصوصی، تفاوت محسوسی نداشته و هر دو بسته به مبانی حسابداری مورد استفاده، از اصول و استانداردهای حسابداری مشابهی استفاده می‌نمایند. ویژگی‌های محیطی حاکم بر فعالیت‌های حاکمیتی بخش عمومی، نحوه تحصیل منابع برای تأمین هزینه این فعالیت‌ها، حقوق شهروندان مبتنی بر پاسخ‌خواهی در خصوص نحوه و محل مصرف منابع، نیازهای اطلاعاتی استفاده‌کنندگان از گزارش‌های مالی، الزام مقامات منتخب به پاسخگویی مالی و غیره از مصادیقی هستند که به نحوی از انحاء در شیوه گزارشگری مالی، نوع و میزان افشاء اطلاعات در این گزارش‌ها، اثرگذار خواهد بود.

در ایالات متحده، سه نوع دولت محلی، ایالتی و فدرال وجود دارد؛ دولت‌های محلی و ایالتی از معیارهای هیئت استانداردهای حسابداری دولتی (GASB) و به خصوص مباحث بیانیه‌های 34 و 44 که شامل گزارش مالی جامع سالانه دولت (CAFR) می‌شود و دولت فدرال از معیارهای هیئت مشورتی استانداردهای حسابداری دولت فدرال (FASAB) برای گزارشگری مالی استفاده می‌کنند. هدف متداول روش‌های حسابداری و گزارشگری مالی در دولت‌های ایالتی و محلی، ارائه‌ اطلاعات سوابق عملکرد نهادهای دولتی به کاربران صورت‌های مالی بوده است تا تصویر کلی از وضعیت مالی این نهادها را در تاریخ‌های مشخص و نمایی پس‌نگرانه از نتایج عملیات این نهادها را در یک بازه زمانی خاص (معمولاً یک ساله) به این کاربران ارائه کنند. هدف مقاله حاضر آن است تا دیدگاه‌ها را نسبت به اطلاعات آینده‌نگر تشریح نماید و از طرفی به کاربران گزارش‌های مالی دولتی نشان داده شود که چطور می‌توانند از این نوع اطلاعات برای ارزیابی بهتر سلامت مالی فعلی هر دولتی و هم‌چنین توانایی آن برای انجام تعهدات خود در آینده استفاده کنند. همچنین کاربرد این اطلاعات در شرکت‌ها و بازار سرمایه نیز محسوس بوده و مطالعات نشان داده است که افشای اطلاعات آینده‌نگر، از یک طرف موجب کاهش نوسانات بازده سهام شرکت‌ها می‌شود و از طرف دیگر با ریسک حسابداری شرکت‌ها در ارتباط است.

Type-II superlattices (T2SLs) are emerging as next-generation materials for infrared detectors. The epitaxial quality of T2SLs is of great importance to the performance of infrared detectors such as dark current and detectivity. Herein, we explore the effect of the native GaSb oxide layer on the surface morphology and crystal quality of InAs/GaSb T2SLs grown with molecular beam epitaxy. The experimental results demonstrate that the thickness of the oxidation layer on GaSb substrates gradually increases over time and is saturated at around 73 Å in the natural oxidation condition. Moreover, the oxidation process is sensitive to humidity. As the thickness of the GaSb oxide layer increases from 18.79 Å to 61.54 Å, the full width at half maximum of the first satellite peak increases from 38.44 to 61.34 arcsec in X-ray diffraction measurements, and the root mean square roughness increases from 0.116 nm to 0.171 nm in atomic force microscopy measurements. Our results suggest that the thickness of the GaSb oxide layer should be less than 55 Å to obtain smooth buffer layers and qualified superlattices. The work provides an optimized direction for achieving high-quality superlattices for infrared optoelectronic devices.

Epitaxially regrown electrically pumped photonic crystal surface‐emitting lasers (PCSELs) emitting near 2 and 2.6 μm are designed, fabricated, and characterized. A high‐index‐contrast photonic crystal layer is incorporated into the GaSb‐based laser heterostructure by air‐hole‐retaining epitaxial regrowth. A square lattice of triangular holes is etched in the top waveguide core layer of the incomplete laser heterostructure. The nanopatterned surface is subsequently cleaned and regrown with AlGaAsSb p‐cladding material. Transmission electron microscopy studies demonstrate uniform regrowth over the nanopatterned GaSb surface. The selected regrowth regimes yield a buried 2D array of elongated air‐holes. The diode PCSELs based on moderately etched nanopatterns demonstrate band‐edge lasing near 2 μm up to room temperatures. The cascade diode PCSELs operate near 2.6 μm with minimum threshold current densities of about 500 A cm−2 achieved at 180 K. The devices generate mW level output in narrow divergence beam emitted from the window in substrate contact. The angle‐resolved electroluminescence measurements reveal a four‐sub‐band band structure with an apparent photonic bandgap corresponding to the buried high‐index‐contrast square photonic crystal layer. The PCSELs made of heterostructures supporting two modes in the vertical direction demonstrate two sets of sub‐bands showing anti‐crossing‐like interaction. [ABSTRACT FROM AUTHOR]

In a solar thermophotovoltaic (STPV) system, TPV cells only use part of the energy emitted by the emitter, and most of the energy is wasted in the form of high-temperature thermal radiation. To completely utilize the high-temperature thermal radiation to improve the efficiency of the STPV system, a hybrid solar thermophotovoltaic-thermoelectric (STPV-TE) system is proposed. The non-contact installation method of the TPV cell and TE module eliminates the temperature interaction between them. The theoretical model and analysis method of the hybrid STPV-TE system are established. The STPV-TE experimental system consists of a commercial GaSb TPV cell and Bi 2 Te 3 TE module. The experimental results showed that the STPV-TE system can promote the efficiency of the STPV system. The total efficiency of the STPV-TE system amounts to 5.91%, of which the TPV cell efficiency of 1.06% and the total efficiency of the four TE modules efficiency is 4.85%. The efficiency of the solo STPV system is 1.44%. The design method of the hybrid STPV-TE system proposes a new method of constructing the STPV-TE system. [ABSTRACT FROM AUTHOR]

Self-assembled GaSb/GaAs quantum-ring-with-dot structures (QRDSs) are the nanostructures exhibiting type-II band alignment. Each QRDS consists of both quantum ring (QR) and quantum dot (QD) parts which have their own energy levels. In this work, the carrier dynamics in the GaSb/GaAs QRDSs are explored and quantitatively described by a rate equation model which is developed from experimental photoluminescence (PL) spectra in literature. The model is comprised of the carrier transition rates and activation energies involved the transfer processes of thermal-excited carriers. The difference between the QR and QD PL intensities is also taken into account in the model. Electronic structures of a single QRDS are calculated in order to determine the overlap between electron and hole wave functions that can be used for estimating the radiative transition rates. Numerical values of the radiative and non-radiative transition rates, carrier capture and escape rates, and activation energies are presented. The PL spectra obtained from the model are consistent with the reported experimental data. [ABSTRACT FROM AUTHOR]

Gallium antimonide (GaSb) is considered an ideal substrate for heterostructure growth via molecular beam epitaxy. A significant aspect that inhibits the widespread application of infrared plane-array detector growth on GaSb is the starting substrate surface quality. In this study, the chemical mechanical polishing of GaSb wafers is investigated by considering the effects of the polishing pad, polishing solution, polishing time and pH buffer on their surface morphology and roughness. The surface morphology and root mean square (RMS) roughness of the free-standing wafers are characterized using a white light interferometer, a laser interferometer and an atomic force microscope. X-ray tomography is employed to measure the surface crystalline quality and strain defects of the samples subjected to the polishing treatments. The results show that with the optimum polishing condition, the polished GaSb wafers demonstrate high-quality surfaces without haze, scratches or strain defect regions. The peak to valley value is 5.0 μm and the RMS roughness can be controlled at less than 0.13 nm. A buffer layer grown on the GaSb surface with molecular beam epitaxy is examined via atomic force microscopy and high-resolution X-ray diffraction, which show a low RMS roughness of 0.159 nm, a well-controlled two-dimensional growth mode and a full width half maximum of the Bragg diffraction peak of 14.2”, indicating high-quality GaSb wafers. Thus, this work provides useful guidelines for achieving GaSb wafers with high-quality surfaces that show significant promise for substrate applications.

Gallium antimonide (GaSb)-based devices operate efficiently in the infrared region. Investigating the toxicity of GaSb thin film is necessary for using embedded GaSb-based devices in living organisms. In this study, viability, oxidative stress, inflammatory responses, apoptosis induction and genotoxicity of GaSb were assayed using L929 cells following a 24 h exposure to GaSb. GaSb thin films were deposited on a quartz substrate using radio frequency (RF) magnetron sputtering. These films were soaked in cell culture medium to prepare test solutions. The viability of cells treated with the GaSb extract was lower than that of control cells. GaSb elicited little reactive oxygen species (ROS) generation. Tumor necrosis factor (TNF)- α and interleukin (IL)-1 β levels were elevated in GaSb-treated cell culture supernatants. Apoptosis and genotoxicity were not evident following GaSb treatment. Overall, these results demonstrate the low toxicity of GaSb compared with previous studies examining arsenic-containing III–V materials, which is desirable for biological devices. [ABSTRACT FROM AUTHOR]