Search

The structural and optical properties of InAsxP1-x metamorphic buffers grown by metal–organic chemical vapor deposition on InP (100) substrates have been investigated. High-resolution X-ray reciprocal space mapping around the (115) InP lattice point reveals that the strain relaxations of the InAsxP1-x with x = 0.5, 0.55, and 0.7 are 98%, 92%, and 96%, while the lateral correlation lengths are 17, 62, and 28 nm, respectively. The optical bandgap energy of the InAsP derived from photoreflectance (PR) measurements decreases from 0.819 to 0.621 eV at 300 K when increasing As composition from x = 0.5 to 0.7. The bowing parameter for the optical bandgap of the InAsP is increased with increasing As composition, which is attributable to the increased spontaneous CuPt-type ordering in InAsP. It is found from the excitation power-dependent PR measurement that the InAsxP1-x layers have different degrees of the bandgap redshift due to the reduced thermal conductivity caused by crystal imperfections generated during the strain relaxation process.

We report on the fabrication of wholly polymeric one-dimensional (1-D) photonic crystals (i.e., Bragg reflectors, Bragg mirrors) via solution processing for use in the near (NIR) and the short wave (SWIR) infrared spectrum (1–2 μm) with very high reflectance (R ∼ 90–97%). Facile fabrication of these highly reflective films was enabled by direct access to solution processable, ultrahigh refractive index polymers, termed, Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs). The high refractive index (n) of CHIPs materials (n = 1.75–2.10) allowed for the production of narrow band IR Bragg reflectors with high refractive index contrast (Δn ∼ 0.5) when fabricated with low n polymers, such as cellulose acetate (n = 1.47). This is the highest refractive index contrast (Δn ∼ 0.5) demonstrated for an all-polymeric Bragg mirror which directly enabled high reflectivity from films with 22 layers or less. Facile access to modular, thin, highly reflective films from inexpensive CHIPs materials offers a new route to ...

We demonstrated the feasibility of using InP (100) substrates, a different indium source, for the synthesis of In2O3 nanowires by the vapor–liquid–solid (VLS) method using a 20-nm-thick Au layer as a catalyst. By varying the thickness of the Au layer and the growth temperature (T), the nanowires showed different morphologies. The nanowires grew along the (100) direction and had perfect crystallinity and lengths up to several hundreds of micrometers. The configured field-effect transistor revealed an n-type behavior with 115 μA of the drain-source current, IDS, under 1.0 V of gate voltage, VDS, at 1.33 × 10−4 kPa of pressure and temperature of 20°C. This result indicates that it is feasible to use different In sources to synthesize In2O3 nanowires by the VLS method for electronic devices.

New high-k gate dielectrics are highly necessary in facilitating the continuous down-scaling of metal–oxide–semiconductor devices to the sub-10 nm range. This study presents ultrathin organic hydrocarbon (HC) films as a novel high-k gate insulator for metal–insulator–semiconductor (MIS) devices. During inductively-coupled plasma chemical vapor deposition with CH4 and H2 gases, the growth temperature greatly affects the structure of the carbon layers and consequently their dielectric characteristics. Specifically, sp2-rich dielectric HC layers are formed below 600 °C, whereas highly-ordered sp2-hybridized graphene is formed at 950 °C. The k value of the resulting HC films increases up to a maximum value of 90 at 350 °C. Moreover, the MIS devices exhibit excellent gate-insulating properties, including almost no hysteresis in the capacitance–voltage curve, low leakage current, and high dielectric strength, which surpass those of existing high-k gate oxides. These results reveal that the organic HC films are a promising next-generation high-k gate dielectric material for sub-10 nm node Si and organic semiconductor technologies.

The morphology of MoS2 nanostructures was manipulated from thin films to vertically aligned few-layer nanosheets on graphene, in a controllable and practical manner, using metalorganic chemical vapor deposition. The effects of graphene layer and MoS2 morphology on photoelectrochemical (PEC) performance were systematically studied on the basis of electronic structure and transitions, carrier dynamic behavior, and PEC measurements. The heterojunction quality of the graphene/vertical few-layer MoS2 nanosheets was ensured by low-temperature growth at 250−300 °C, resulting in significantly improved charge transfer properties. As a result, the PEC photocurrent density and photoconversion efficiency of the few-layer MoS2 nanosheets significantly increased upon the insertion of a graphene layer. Among the graphene/MoS2 samples, the few-layer MoS2 nanosheet samples exhibited shorter carrier lifetimes and smaller charge transfer resistances than the thin film samples, suggesting that vertically aligned nanosheets provide highly conductive edges as an efficient pathway for photo-generated carriers and have better electronic contact with graphene. In addition, the height of vertical MoS2 nanosheets on graphene should be controlled within the carrier diffusion length (~200 nm) to achieve the optimal PEC performance. These results can be utilized effectively to exploit the full potential of two-dimensional MoS2 for various PEC applications.

A controllable approach that combines surface plasmon resonance and two-dimensional (2D) graphene/MoS2 heterojunction has not been implemented despite its potential for efficient photoelectrochemical (PEC) water splitting. In this study, plasmonic Ag-decorated 2D MoS2 nanosheets were vertically grown on graphene substrates in a practical large-scale manner through metalorganic chemical vapor deposition of MoS2 and thermal evaporation of Ag. The plasmonic Ag-decorated MoS2 nanosheets on graphene yielded up to 10 times higher photo-to-dark current ratio than MoS2 nanosheets on indium tin oxide. The significantly enhanced PEC activity could be attributed to the synergetic effects of SPR and favorable graphene/2D MoS2 heterojunction. Plasmonic Ag nanoparticles not only increased visible-light and near-infrared absorption of 2D MoS2, but also induced highly amplified local electric field intensity in 2D MoS2. In addition, the vertically aligned 2D MoS2 on graphene acted as a desirable heterostructure for efficient separation and transportation of photo-generated carriers. This study provides a promising path for exploiting the full potential of 2D MoS2 for practical large-scale and efficient PEC water-splitting applications.

We have investigated the structural characteristics and the device performance of three-stack InGaAsSb/AlGaAsSb quantum-well (QW) light-emitting diodes (LEDs) grown by using molecular beam epitaxy. The QW LED structure with an 8-nm well thickness had a single peak emission wavelength of 2.06 μm at an injection current of 0.3 A at room temperature. However, the QWLEDs with three different well thicknesses of 5-, 10-, and 15-nm had double peak emission wavelengths of 1.97 and 2.1 μm at an injection current of 1.1 A, which were associated with the radiative recombination in the QW with a 5-nm well thickness and the overlapped emission from the QWs with 10- and 15-nm well thicknesses, respectively.

We investigated the oncologic outcomes by intrinsic subtype and age in young breast cancer patients and whether survival differences were related to treatment changes over time. A retrospective analysis was performed on 9633 invasive breast cancer patients treated at Asan Medical Center from January 1989 to December 2008. We also enrolled a matched cohort adjusting for tumor size, lymph node metastasis, subtypes, and tumor grade. Patients aged

We report on the synthesis of few−layers MoS2 flakes coated on the p−Si nanorods (p−SiNRs) via the metalorganic chemical vapor deposition (MOCVD) method. The MoS2 flakes show a vertically−standing, few−layers (10–15) morphology. The photoluminescence characteristic of the MoS2/p−SiNRs heterojunction exhibits a blue−shift energy bandgap (1.65−1.78 eV) at temperature of 77 K with thinner MoS2 layers due to the quantum confinement effect. As a result, the fabricated MoS2/p−SiNRs photocathode results in a saturated photocurrent density (PCD) and a photoconversion efficiency (η) of 42.3 mA cm−2, and 0.64% at 0 V (vs. RHE), respectively. Due to the built−in potential of heterojunction and more active edge sites, the onset voltage of the MoS2/p−SiNRs sample was positively shifted to ~0.72 V (vs. RHE). Based on this finding, we suggest that a heterojunction structure might serve an approach for fabricating the hybrid photoelectrochemical (PEC) device of the Si−based material.

Two-dimensional (2D) SnS2 nanosheets vertically grown on graphene electrodes have still not been demonstrated despite their considerable research interest and potential for photoelectrochemical (PEC) applications. Herein, the controllable growth and enhanced PEC water-splitting performance of vertically aligned 2D SnS2 nanosheets on graphene are reported. The heterojunction quality of the graphene/2D SnS2 nanosheets was ensured by low-temperature growth at 230 °C using metalorganic chemical vapor deposition, resulting in significantly improved charge transfer properties. The PEC photocurrent density and photoconversion efficiency significantly increased upon insertion of a graphene layer. In addition, the 2D SnS2 nanosheet microscopic structure dependency of the PEC performance was systematically studied. The best PEC reactivity of the 2D SnS2 nanosheets was achieved at a height of ∼0.85 µm, corresponding to nearly the limit of the carrier diffusion length, and a thickness of ∼70 nm to balance the low interfacial contact resistance with an effective photogenerated carrier dynamics. These results, including the low-temperature vertical growth of 2D SnS2 on graphene, can effectively be utilized to exploit the full potential of 2D SnS2 for various PEC applications.

Tin sulfide (SnS) is known for its effective gas-detecting ability at low temperatures. However, the development of a portable and flexible SnS sensor is hindered by its high resistance, low response, and long recovery time. Like other chalcogenides, the electronic and gas-sensing properties of SnS strongly depend on its surface defects. Therefore, understanding the effects of its surface defects on its electronic and gas-sensing properties is a key factor in developing low-temperature SnS gas sensors. Herein, using thin SnS films annealed at different temperatures, we demonstrate that SnS exhibits n-type semiconducting behavior upon the appearance of S vacancies. Furthermore, the presence of S vacancies imparts the n-type SnS sensor with better sensing performance under UV illumination at room temperature (25 &deg, C) than that of a p-type SnS sensor. These results are thoroughly investigated using various experimental analysis techniques and theoretical calculations using density functional theory. In addition, n-type SnS deposited on a polyimide substrate can be used to fabricate high-stability flexible sensors, which can be further developed for real applications.

This article presents data obtained from the atomic force microscopy (AFM) images of ultrathin high-k hydrocarbon (HC) films. The high-k HC films were synthesized on Si(100) wafers at various growth temperatures by using inductively-coupled plasma chemical vapor deposition with CH4 gas and a gas mixture consisting of 10% H2 and 90% Ar. The AFM images were obtained by tapping mode. The AFM results provide the surface topography, roughness, and thickness of the HC films as a function of growth temperature, which are essential data for high-k gate dielectrics of metal-insulator-semiconductor device applications. This data article is related to the article entitled, “Novel high-k gate dielectric properties of ultrathin hydrocarbon films for next-generation metal-insulator-semiconductor devices” (Kim et al., 2020) [1] .

In this paper, we report the synthesis results of Ga2O3 semiconductor nanowires (NWs) on GaAs (100) semi-insulator substrate by vapor liquid solid (VLS) method. Our study based on Ag nanoparticle (AgNP) catalyst, in which prepared by conventional sol–gel method. As the GaAs wafer, after being deposited an AgNP layer in HF/AgNO3 aqueous solution, which dried and loaded to vacuum-chamber. GaAs slices heated in vacuum-furnace by VLS method with two temperature modes. The results showed that the Ga2O3 NW morphologies and properties depend strongly on technological conditions, such as AgNP catalyst concentration, growth temperature, and vapor pressure. It is also indicated that the NW random grown over large area with the diameter in the region conform from 18 to 30 nm scale and lengths ranging from several tens of nm to a few hundred micrometers.

This study analyzed results of the causes of failure in 1,022 fire trucks currently being used in South Korea (aerial ladder, aerial platform, pumper, and chemical fire trucks). The results show that 46% of aerial ladder trucks have defective in the elevator brake systems, 29% of aerial platform trucks have contamination in the hydraulic oil, 37% of pumpers have defective in the pneumatic cylinders of the air supply system, and 39% of chemical fire trucks have defective in the powder fire extinguishing systems. The principal reasons for malfunctions are deterioration of the apparatuses, and accumulated fatigue from repetitive use of certain components, such as pneumatic cylinders in the air supply system and wire rope jamming in rollers in the ladder apparatus. These manufacturing defects should be improved upon in the manufacturing process. As a result, the fire trucks, which are used for 5 years or more, need precise inspections in accordance with the Regulation on Fire Apparatus Maintenance. Fire apparatuses have a service life of 10 to 12 years or more. They need to be replaced or require life extension, and they should be kept in top shape with the best maintenance for public safety.

The dye-sensitized solar cell (DSC) has attracted considerable attention as a next-generation solar cell because of its many virtues such as low fabrication cost, environmentally benign process, glossy transparency, and relatively high energy conversion efficiency. One of the issues with DSCs is the need to improve the transfer of electrons into the redox system to activate electrolyte reduction at the counter electrode (CE). Pt is traditionally the most popular material for the CE of DSCs, and numerous substitutes, such as carbon nanotubes (CNT), CNT–TiN, and CNT–Pt materials, have been developed to replace or reduce the amount of expensive Pt used. Owing to its unique 2D structure, large specific surface area, high electrical conductivity, and robust mechanical strength, graphene is known as one of the best supports for metal nanoparticles (NPs) for applications in energy conversion/storage devices. Graphene–metal composites have mostly been synthesized through either chemical or physical methods. However, extreme conditions such as high temperature, low pressure, a liquid environment, and chemical toxicity become drawbacks for the application of graphene–metal composites in large-scale production. Recently, we developed a new process for efficiently synthesizing supported PtNPs by using dry plasma reduction (DPR) near room temperature under atmospheric pressure. The aim of this technique was to overcome the previously mentioned process restrictions. Herein, we demonstrate the use of DPR to synthesize PtNPs on chemical vapor deposition (CVD)-grown graphene under atmospheric pressure, without using any toxic chemicals, near room temperature. The aim of this study was to develop transparent and efficient DSCs, which are crucial for realizing building-integrated photovoltaics (BIPVs), through synergistically combining the high transparency of CVD-grown graphene and the low charge-transfer resistance of supported PtNPs by using methods that keep the production cost low. The synthesis of Pt NPs hybridized on CVD-grown graphene was achieved by using DPR, as shown in Scheme 1. First, a drop of precursor solution was loaded on the substrate, followed by complete drying of the solvent at 70 8C for 10 min. During this drying process, H2PtCl6.xH2O was partially reduced

We report the spectral response characteristics of a dual–band infrared photodetector based on nBn photodiode configuration–with GaSb and InGaAsSb absorption layers and a ternary layer of AlGaSb that serves as unipolar barrier in between—which has independent access to both sides. The resulting structure has detection capability in the short-wavelength infrared ranges, cut-off wavelength of 1.6 μm (SWIR1; GaSb) and 2.65 μm (SWIR2; InGaAsSb) depending on the applied bias. The dual-band photodetector was evaluated by current–voltage (I–V) characteristics, spectral response, and detectivity (D*). The measured values of D* at 300 K were 2.3 × 1012 cm·Hz1/2·W−1 (at 1.5 μm) and 2.1 × 1011 cm·Hz1/2·W−1 (at 2.25 μm).

C under a sulfur-poor environment, i.e. a Cd to Smolar ratio of 1/0.125. Photoluminescence studies showed that all CdS films we studied had asignificant amount of sulfur vacancies and that those vacancy energy states were responsible forthe high photoconductivity values. Both dark and photo sheet resistance values were lower when ahigher NH

We report the light-emitting diode (LED) characteristics of colloidal core-shell CdSe/ZnS nanocrystal quantum dots (QDs) embedded in TiO2–δ thin films on Si substrate. High-quality CdSe/ZnS QDs were synthesized via a pyrolysis in the range of 220–280 °C. The QDs were embedded in TiO2–δ thin film at 200 °C by plasma-enhanced metallorganic chemical vapor deposition. The diode structure of n-TiO2–δ/QDs/p-Si showed electroluminescence characteristics, indicating the possibility of LED applications of colloidal CdSe/ZnS nanocrystal QDs embedded in oxide films on large-area Si wafer. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

【We report on the light-emitting diode (LED) characteristics of core-shell CdSe/ZnS nanocrystal quantum dots (QDs) embedded in $TiO_2$ thin films on a Si substrate. A simple p-n junction could be formed when nanocrystal QDs on a p-type Si substrate were embedded in ${\sim}5\;nm$ thick $TiO_2$ thin film, which is inherently an n-type semiconductor. The $TiO_2$ thin film was deposited over QDs at $200^{\circ}C$ using plasma-enhanced metallorganic chemical vapor deposition. The LED structure of $TiO_2$ /QDs/Si showed typical p-n diode currentvoltage and electroluminescence characteristics. The colloidal core-shell CdSe/ZnS QDs were synthesized via pyrolysis in the range of $220-280^{\circ}C$ . Pyrolysis conditions were optimized through systematic studies as functions of synthesis temperature, reaction time, and surfactant amount.】

We studied systematically various Bi-based pyrochlore materials (Bi3NbO7, Bi2Ti2O7, Bi2Mg2/3Nb4/3O7, Bi2Cu2/3Nb4/3O7, and Bi1.5Zn1.0Nb1.5O7) prepared by pulsed-laser deposition at less than 150°C for potential dielectric applications for organic thin film transistor (OTFT). The p-type pentacene OTFT devices were fabricated with 200 nm-thick Bi2Mg2/3Nb4/3O7 (BMN) with a high dielectric constant (∼ 40) as gate dielectrics. The channel width and length of the OTFT devices were 50 and 1000 μ m, respectively. The OTFT operating voltage of 5V could be possible with the low threshold voltage of ∼ 1 V due to high dielectric constant and capacitance values (209 nF/cm2) of BMN thin films. Such a low operating voltage and the mobility as high as ∼ 1.2 cm2/Vs indicate that low-temperature grown Bi-based pyrochlore materials, i.e., BMN, are very promising for gate dielectric applications of OTFT.

The 5 nm thick nanomixed Ga2O3-TiO2 films were deposited at 200°C on Si (001) substrates using plasma-enhanced atomic-layer deposition for gate dielectric applications. The Ga2O3-TiO2 films still remain in amorphous phase after thermal annealing at 800°C due to Ga2O3 acting as a crystallization inhibitor in the nanomixed films. The equivalent oxide thickness (EOT) of 6 A of the TaN/Ga2O3-TiO2/Si capacitors was not changed significantly till annealing temperature of 700°C. Above 700°C, however, the EOT was increased with increasing annealing temperature probably due to enhanced interfacial layer formation. The capacitors annealed at 1000°C exhibit a leakage current density of approximately 4 × 10− 3 A/cm2 at −1.5 V and an interfacial charge density of 1.5 × 1011 cm− 2eV− 1. These results indicate that the Ga2O3-TiO2 nanomixed films are a new potential candidate for gate dielectric applications.

The degradation of reinforced concrete (RC) structures due to physical and chemical attacks has been a major issue in construction engineering. Deterioration of RC structures by chloride attack followed by reinforcement corrosion is one of the serious problems. An objective of this study is to develop a form of mathematical model of chloride ingress into concrete. In order to overcome some limits of the previous approaches, a chloride ingress model, consisting of chloride solution intrusion through the capillary pore and chloride ion diffusion through the pore water, was proposed. Moreover, the variability of chloride ion diffusivity due to the degree of hydration of cement, relative humidity in pore, exposure condition, and variation of chloride binding, was considered in the model. In order to verify the proposed model, the results predicted by the proposed model were compared with analysis results of Life-365, a computer program for predicting the service life of reinforced concrete structures exposed to chlorides. In conclusion, the proposed model would be promising to predict the chloride ion profile and to estimate the service life of RC structures.

We report InAs quantum dot infrared photodetectors that utilize In0.15Ga0.85As strain-relief cap layers. These devices exhibited normal-incidence photoresponse peaks at 8.3 or 8.8 μm for negative or positive bias, respectively. At 77 K and −0.2 V bias the responsivity was 22 mA/W and the peak detectivity D* was 3.2×109 cm Hz1/2/W.

An InAs/AlGaAs quantum-dot infrared photodetector based on bound-to-bound intraband transitions in undoped InAs quantum dots is reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 /spl mu/m. At 77 K and -0.7 V bias, the responsivity was 14 mA/W and the detectivity, D*, was 10/sup 10/ cm/spl middot/Hz/sup 1/2//W.

We report on a study of n-type quantum dot (QD) infrared photodetectors (QDIPs) based on InAs/GaAs QDs grown via an innovative technique called punctuated island growth. The electronic structure of the QDs inserted in QDIP devices is comprehensively investigated with photoluminescence, and intra- and interband photocurrent spectroscopy. The influence of AlGaAs layers inserted in active regions on the performance of the QDIPs is examined. Bias and temperature dependence of intraband photoresponse of QDIPs with undoped active region is examined. Initial results on intraband photoresponsivity and detectivity of these QDIPs at 77 K are reported.

We have performed a comprehensive investigation of n-type quantum dot infrared photodetectors (QDIPs) based on InAs/GaAs epitaxical island quantum dots (QDs) grown via the innovative punctuated island growth technique. The structural properties of the QDs were investigated with cross-sectional transmission electron microscopy and atomic force microscopy. The electronic properties of the QDs inserted in QDIP devices were investigated with photoluminescence (PL), PL excitation, and intra- and inter-band photocurrent spectroscopy. The influence of AlGaAs layers inserted into the QDIP active regions on the performance of dark current and inter- and intra-band photocurrent was examined. Initial results on intra-band responsivity and detectivity of these QDIPs at 77 K with undoped active region show promise for application.

Combined inter- and intra-band spectroscopy studies are presented on structurally well-characterized InAs/GaAs(001) self-assembled quantum dots grown via conventional continuous deposition and the innovative punctuated island growth approach. Temperature and power dependent photoluminescence (PL) and PL Excitation (PLE) on these remarkably uniform quantum dot based samples (with typical PL linewidth 25 meV), reveal details of size-dependent electronic structure. These studies are complemented with systematic near- and middle-infrared photocurrent spectroscopy for interband through electron intra-band transitions as a function of temperature and applied electric field.

We report a high detectivity of 3×1011 cm Hz1/2/W at 78 K for normal-incidence quantum dot infrared photodetectors with ten layers of undoped InAs/InGaAs/GaAs quantum dot active regions. The high detectivity seen at 1.4 V corresponds to photoresponse peaks at 9.3 and 8.7 μm for positive and negative bias, respectively.

We report noise characteristics, carrier capture probability, and photoconductive gain of InAs quantum-dot infrared photodetectors with unintentionally doped active regions. At 77 K, a photoconductive gain of 750 was observed at a bias of 0.7 V. The high gain is a result of the low carrier capture probability: p=0.0012.

We studied both cw and time-resolved photoluminescence of colloidal CdSe/ZnS core-shell quantum dots capped with chemical ligands. For the trioctylphosphine oxide capped CdSe/ZnS QDs, both the luminescence intensity and lifetime were found to be increased with increasing temperatures, which can be explained by the thermal activation of the carriers trapped at shallow trapping centers. After the ligand exchange into 3-mercaptopropionic acid, the non-radiative recombination rate was increased and the luminescence efficiency was decreased at room temperature. When the QDs were employed in photovoltaic devices, photocurrent was found to be increased after the ligand exchange. The improved photocurrents observed in photovoltaic devices can be explained by the improved tunnelling probability between the neighbouring QDs. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4745080]

To further the objective of controlled manipulation of the electronic states in epitaxial island quantum dots (QDs), we introduce the notion of a lateral potential confinement layer (LPCL) whose judicious placement during island capping allows selective impact on ground and excited electron and hole states. The energy states of InAs/In0.15Ga0.85As QDs are manipulated using 10-monolayer-thick In0.15Al0.25Ga0.60As LPCLs positioned at the bottom, upper, and top region of the QDs. The changes in the photoluminescence (PL) and PL excitation spectra reveal the nature of the electronic transitions impacted selectively through the spatial charge distributions of the states involved.

We report a bias-controllable multiwavelength quantum dot infrared photodetector (QDIP). The active region of the QDIP consisted of five layers of InAs quantum dots with InGaAs cap layers. Photoresponse peaks at 5.5, 5.9, 8.9, and 10.3–10.9 μm were observed. The relative response of these peaks could be controlled through the applied bias. For 5.9 μm detection, a peak detectivity, D*, of 5.8×109 cm Hz1/2/W at 77 K and 0.3 V was achieved.

We report the realization of electron intraband absorption based middle- (∼5.6 μm) and long- (∼10 μm) wavelength infrared (IR) photoresponse for normally incident radiation on InGaAs-capped GaAs(001)/InAs quantum dots (QDs) in a n–i(QD)–n structure. The relative photoresponse in this dual-wavelength structure is tunable up to two orders of magnitude with bias. The full width at half maximum of the long-wavelength IR intraband photocurrent peak at 80 K is as narrow as 8.2 meV.

We report on tailoring detection bands of InAs quantum-dot infrared photodetectors (QDIPs) using InxGa1−xAs strain-relieving capping layers that also act as quantum wells (QWs). QDIPs with InAs QDs capped by a 20 ML In0.15Ga0.85As QW show a sharp photoresponse at ∼9 μm, while the counterpart QDIPs without QWs show broad photoresponse in the 5–7 μm range. The excited states involved in the intraband transitions in QDIPs with the In0.15Ga0.85As QW appear to be coupled QD and QW electron excited states.

This study reports the effect of doping level on the performance of InAs/GaAs quantum-dot infrared photodetectors (QDIPs). Two QDIP samples were prepared via molecular beam epitaxy: n+-i(QDs)-n+ QDIP with undoped quantum dot (QD) active region, referred to as undoped QDIP, and n+-n(QDs)-n+ QDIPs intended to contain two electrons per QDs, referred to as doped QDIP. InAs self-assembled QDs were grown on GaAs (001) wafers by three mono-layers of InAs deposition. Both QDIPs showed a photoluminescence peak at 1.182 μm as well as a similar broad photocurrent (PC) spectrum peaked at about 7.5 μm, ranging from 4 μm to 9 μm at 5 K. Undoped QDIP yielded a PC spectrum of up to 100 K, whereas doped QDIP had a PC spectrum of up to 40 K only. This finding was mainly attributed to the lower dark current properties of undoped QDIP. Undoped QDIP at 77 K showed five orders of magnitude lower than the dark current of doped QDIP at 5 K.

This paper reviews recent progresses in developing self-assembled InAs/GaAs quantum dots based infrared photodetectors, especially, with n-i(QDs)-n configuration. These significant progresses indicate a realistic hope that QDIPs can be exploited for mid-infrared imaging application.

We report a series of InAs quantum dots infrared photodetectors. By using InGaAs cap layers and InAIGaAs lateral potential confinement layers, the peak absorption can be manipulated in from /spl sim/5.6 /spl mu/m to /spl sim/9 /spl mu/m.

In this paper, we present a study of a series of InAs quantum dot infrared photodetectors (QDIPs) with unintentionally doped active regions. The wavelength tunability will be demonstrated by changes of the content of In and Al in the InGaAs cap layers and InAlGaAs lateral potential confinement layers. The samples were grown on semi-insulating GaAs(001) substrates by solid-source molecular beam epitaxy (MBE). Fourier transformation infrared (FTIR) spectroscopy measurement demonstrated peak photoresponses at the wavelength ranging from /spl sim/ 5.6 /spl mu/m to /spl sim/ 9 /spl mu/m. The dark current and noise of the QDIP samples were measured at various temperature.

We report on normal-incidence single and dual-wavelength intraband infrared photodetectors (with contacts in the vertical configuration) based on epitaxial InAs/InAlGaAs quantum dots.

This paper surveys recent work in several photodetector areas including high-speed, low-noise avalanche photodiodes, high-power photodiodes, solar-blind ultra-violet PIN photodiodes, and quantum dot infrared photodetectors (QDIPs).

This paper surveys recent work in several photodetector areas including high-speed, low-noise avalanche photodiodes, solar-blind ultra-violet PIN photodiodes, and quantum dot infrared photodetectors (QDIPs).

Manipulation and control of the electronic structure of quantum dots (QDs) is of central importance to their applications in electronics and optoelectronics. Such tuning is typically carried out by varying the QD average size and shape, or the capping layer, or annealing QDs thermally. Most these approaches do not allow selective tuning some QD states but not others. In this report, we introduce and demonstrate a mean of achieving selective tuning of energy levels through the use of a thin layer, called here the lateral potential confinement layer (LPCL), positioned at the bottom, upper, or top regions of the QDs.