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Abstract This study investigates the development of InAs quantum dot (QD) lasers on a InP(001) substrate, utilizing only III‐arsenide layers. This approach avoids the issues associated with the use of phosphorus compounds, which are evident in the crystal growth of conventional C/L‐band QD lasers, making the manufacturing process safer, simpler, and more cost‐effective. The threshold current density of the fabricated QD laser was 633 A/cm2, which is the lowest value for QD lasers in the 1.6‐µm wavelength region. This result suggests a high cost‐effectiveness and paves the way towards a large‐scale production technology for high‐performing C/L/U‐band QD lasers.

This study investigates the development of InAs quantum dot (QD) lasers on a InP(001) substrate, utilizing only III‐arsenide layers. This approach avoids the issues associated with the use of phosphorus compounds, which are evident in the crystal growth of conventional C/L‐band QD lasers, making the manufacturing process safer, simpler, and more cost‐effective. The threshold current density of the fabricated QD laser was 633 A/cm2, which is the lowest value for QD lasers in the 1.6‐µm wavelength region. This result suggests a high cost‐effectiveness and paves the way towards a large‐scale production technology for high‐performing C/L/U‐band QD lasers.This study presents a safer, simpler, and more cost‐effective method for producing InAs quantum dot (QD) lasers by using only III‐arsenide layers on an InP(001) substrate, thus circumventing problems with phosphorus compounds. The resulting QD laser exhibited a record low threshold current density of 633 A/cm2 for the 1.6‐μm wavelength region, indicating high cost‐effectiveness and paving the way for large‐scale production of high‐performance C/L/U‐band QD lasers. [ABSTRACT FROM AUTHOR]

This letter reports vacuum annealing of lateral field-plated $\beta $ -Ga2O3 MOSFETs with significant current recovery and improvement in the on-state resistance, $\text{R}_{\text {on}}$ , after Reactive Ion Etching (RIE) induced damage. We fabricate and characterize MOSFETs based on Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) grown $\beta $ -Ga2O3 wafers to better understand the effects of vacuum annealing. We see a clear trend of vacuum annealed devices showing no reduction in breakdown voltages, $\text{V}_{\text {br}}$ , as compared to polymer passivated MOSFETs. This trend holds for identical gate-drain separation, $\text{L}_{\text {gd}}$ , varying from $20 ~\mu \text{m}$ to $60 ~\mu \text{m}$. Devices show up to 10 times reduction in $\text{R}_{\text {on}}$ as compared to previously reported $\text{R}_{\text {on}}$ for SU-8 passivated devices. For MBE sample, $\text{V}_{\text {br}}$ of 7.16 kV for a $\text{L}_{\text {gd}}$ = $40 ~\mu \text{m}$ device, with an average field strength of 1.79 MVcm $^{{-{1}}}$ and peak drain current density of 40 mA/mm, is reported. $\text{R}_{\text {on}}$ is $897 \Omega $. mm, giving Baliga’s Figure of Merit (BFOM) as 5.71 MWcm $^{{-{2}}}$. For a $\text{L}_{\text {gd}}$ = $60 ~\mu \text{m}$ device, we report record high breakdown of 8.56 kV with BFoM of 4.9 MWcm $^{{-{2}}}$. For MOCVD grown sample, a $\text{L}_{\text {gd}}$ = $60 ~\mu \text{m}$ device has $\text{V}_{\text {br}}$ of 6.11 kV, $\text{R}_{\text {on}}$ of 1.98 $\text{k}\Omega $. mm and corresponding BFoM of 1.88 MWcm $^{{-{2}}}$. Transfer Length Method (TLM) analysis indicates incomplete post etch current recovery after vacuum annealing. [ABSTRACT FROM AUTHOR]

We report on a planar long-wavelength infrared photodetector based on InAs/InAs1-xSbx type-II superlattice with zinc diffusion. The superlattice structures were grown by molecular beam epitaxy, followed by a post-growth Zinc diffusion process in a metal-organic chemical vapor deposition reactor. The planar photodetectors showed a peak responsivity of 2.18 A/W, under an applied bias of −20 mV, with a corresponding quantum efficiency of 44.5%, without any anti-reflection coating, and had a 100% cut-off wavelength of $8.5 \mu \text{m}$ at 77 K temperature. These photodetectors exhibit a specific peak detectivity of $3.0\times 10^{12}$ cm.Hz1/2/W, with a dark current density of $1.5\times 10^{-5}$ A/cm2 and the differential-resistance-area product of $\sim 8.6\times 10^{-1} \Omega $.cm2, under an applied bias of −20 mV at 77 K. A comparative study between the planar and conventional mesa-isolated photodetectors was also carried out. [ABSTRACT FROM AUTHOR]

An In0.53Ga0.47As/indium phosphide (InP) avalanche photodiode (APD) with a separate absorption, grading, charge, and multiplication (SAGCM) structure is epitaxially grown by molecular beam epitaxy (MBE). The resulting material is studied using X-ray diffraction (XRD), photoluminescence (PL), and scanning transmission electron microscopy. The activation energy extracted from the dark current of the APD indicates that it is dominated by the generation–recombination (G–R) process. Deep low-temperature PL peaks reveal the existence of an ${E}_{v} + 0.42$ -eV deep energy level defect in the indium–gallium–arsenide (InGaAs) absorber layer, which is considered to be a result of point defects caused by Ga-poor or In-poor MBE growth conditions. The effect of the defect on the dark current is confirmed using numerical calculation methods. [ABSTRACT FROM AUTHOR]

The recent progress in III-nitride tunnel junction (TJ) contacts for optoelectronic devices is summarized in this review paper. Due to the rapid developments of various III-nitride based optoelectronic devices for different emerging applications, TJs are of interest for these devices to achieve more efficient device performance. This review paper first briefly describes the working principles of TJs and the advantages of employing TJs in optoelectronic devices. The significant advancements in III-nitride TJs realized by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are addressed, as well as their TJ device performances. Lastly, the critical challenges for employing III-nitride TJs in wide bandgap ultraviolet (UV) light emitters are discussed for future investigations. [ABSTRACT FROM AUTHOR]

There are vital challenges to harness the unique assets of germanium (Ge) because of Ge-on-insulator (GeOI) processing issues. The advances in molecular beam epitaxy (MBE) technology have enabled the defect-free growth of atomic-level Ge stacks over the standard monolithic silicon platform to leverage the properties of the Ge as a channel layer. Here, we present the first ever report on the authoritative integration of ferroelectric (FE) hafnium zirconium oxide (HZO) over the p-Ge/n-Ge $_{-on-}\text{n}$ -Si system. A rudimentary approach for the carrier modulation in the channel was employed using depletion approximation and negative capacitance (NC) to fabricate HZO and thin p-Ge channel-based FET. The TaN/HZO/TaN stacks were optimized and characterized for enhanced ferroelectricity and non-centrosymmetric orthorhombic phase, which is further confirmed with piezoresponse force microscopic (PFM) analysis. The trivial loop hysteresis conditions to validate the NCFET operation was discussed. The devices demonstrated a lower subthreshold swing (SS) of ~23.44 mV/dec and ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{OFF}}$ ratio of 105. The threshold voltage shift ${V}_{t} = -0.6$ and −1.1 V with the body bias voltage of 0.25 and 0.5 V, respectively. Minimum DIBL measured ~26 mV/V, and rule-out gate induces drain lowering (GIDL) effect due to no gate–drain region overlap. [ABSTRACT FROM AUTHOR]

The use of beryllium as both an i-layer and current spreading layer (CSL) dopant in GaN quasi-vertical p-i-n diodes on sapphire was investigated. With the inclusion of the Be CSL, the current uniformity dramatically improves from $\sim 40$ % of the p-contact radii to 100% resulting in higher breakdown performance and reduced leakage currents. Metal modulated epitaxy (MME) GaN p-i-n diodes on sapphire templates with beryllium-doped GaN (GaN:Be) i-layer thicknesses in the range of 1– $10~\mu \text{m}$ are reported. Additionally, a GaN:Be CSL sandwiched between two conductive Si-doped GaN layers is used to achieve a high quasi-vertical p-i-n diode breakdown voltage of 375 V and a breakdown field of 1.875 MV/cm for the $2~\mu \text{m}$ i-layer p-i-n diodes. At room temperature, the diode with a mesa diameter of $100~\mu \text{m}$ showed a differential ON-resistance (${R}_{ \mathrm{\scriptscriptstyle ON}} \,\,=\,\,\text{d}{V}/\text{d}{I}$) as low as 0.3 $\text{m}\Omega $ -cm2 for a $10~\mu \text{m}$ GaN:Be i-layer diode. A Baliga’s figure of merit (BFOM) ($\text {V}_{\text {Br}}^{{2}}/{R}_{ \mathrm{\scriptscriptstyle ON}}$) of 363 MW/cm2 was achieved for the $10~\mu \text{m}$ i-layer p-i-n diode. This is the highest reported BFOM for GaN p-i-n diodes on foreign substrates. Additionally, the leakage current density is very low: $1\times 10^{{-{9}\,\,{ }}}$ kA/cm2 at 300 V reverse bias for the 5 and $10~\mu \text{m}$ GaN:Be i-layer devices. These devices exhibit a current ON/ OFF ratio ten orders of magnitude. Given the low particle environment, rapid growth rates, ease of compatibility with the toxic dopant Be, and high device performance, the use of Be as a dopant is very useful for high-power devices. [ABSTRACT FROM AUTHOR]

Direct epitaxial integration of magnetic layers with wide bandgap nitride semiconductors will enable spin-controlled transport and photonic phenomena, seeding ideas for functional spintronic devices. Using plasma-assisted molecular beam epitaxy (MBE) in a previously unexplored window, significantly improved ferrimagnetic Mn4N layers are successfully grown on GaN with ~1 nm surface roughness. Distinct from earlier reports, the Mn4N layers grown on GaN are found to be [001] oriented with 12-fold in-plane symmetry in the diffraction pattern. This unique epitaxial registry originates from three equivalent rotational domains. The ferrimagnetic magnetotransport properties of low growth temperature Mn4N layers on GaN are comparable to those reported on cubic substrates such as MgO. However, a sign-flip of the Hall resistance is discovered for Mn4N layers grown above 300 °C. [ABSTRACT FROM AUTHOR]

A cell-averaged constant false alarm rate (CFAR) detector is described and applied to data collected with a multibeam echo sounder (MBES). The CFAR detector is designed specifically for transient targets observed with MBES, and operates under the assumption that background noise, including volume and seafloor reverberation, is locally stationary in time. This assumption, and the CFAR detector performance in general, was examined for data collected by a 30-kHz MBES operating in the Gulf of Mexico where the targets of interest were methane gas bubble plumes rising up from the seabed. Results with example data suggest that the CFAR detector was able to remove 99.1% of the MBES raw data while preserving the targets of interest. False detections appear randomly distributed throughout a single MBES ping, unlike the targets, and a within-ping target clustering algorithm was able to remove many of the false detections. In a single ping, an example is shown where the combined CFAR detector and a target cluster-size rule was able to reduce the number of false detections to 99.8% of the original data. The detector and cluster-size rules were applied to a sequence of approximately 400 pings, and two additional morphological rules based on the size and aspect ratio of the resulting target clusters were then applied to the detections to isolate the MBES backscatter intensity associated with gas bubbles. This combination of CFAR detector and simple morphological classification rules provides a useful way to detect gas bubble seeps or other transient targets. [ABSTRACT FROM AUTHOR]

In this work, we are concerned with the stability and convergence analysis of the second-order backward difference formula (BDF2) with variable steps for the molecular beam epitaxial model without slope selection. We first show that the variable-step BDF2 scheme is convex and uniquely solvable under a weak time-step constraint. Then we show that it preserves an energy dissipation law if the adjacent time-step ratios satisfy rk:= τk/τk−1 < 3.561. Moreover, with a novel discrete orthogonal convolution kernels argument and some new estimates on the corresponding positive definite quadratic forms, the L2 norm stability and rigorous error estimates are established, under the same step-ratio constraint that ensures the energy stability, i.e., 0 < rk < 3.561. This is known to be the best result in the literature. We finally adopt an adaptive time-stepping strategy to accelerate the computations of the steady state solution and confirm our theoretical findings by numerical examples. [ABSTRACT FROM AUTHOR]

Epitaxial SrTiO3 thin films were grown by molecular beam epitaxy (MBE) using an oxygen plasma source. SrO and TiO2 layers were alternately deposited on 0.5 wt% (001) Nb doped SrTiO3 substrates whose surface were terminated with TiO2. A two-dimensional (2-D) layer-by-layer growth mode was confirmed by the reflection high energy electron diffraction (RHEED) oscillation during the growth and the well-terraced SrTiO3 surface was obtained after growth. X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) analysis showed that the obtained SrTiO3 thin films had epitaxially (001) oriented and stoichiometric crystal structures without any interfacial layer. With simple MIS (Metal-Insulator-Semiconductor) capacitors using Ir top electrodes, the dielectric constants of the SrTiO3 thin film with 10, 15, 20, 100 nm were measured at room temperature, 10 kHz and zero bias. [ABSTRACT FROM AUTHOR]

Vertical GaN-on-GaN p-n diodes grown by ammonia molecular beam epitaxy (NH3 MBE) are reported in this letter for prospective high-power application devices. The diodes, consisting of only $4~\mu \text{m}$ drift layer with low unintentional background doping of $\sim 3\times {10}^{{15}}{\mathrm {cm}}^{\text {-3}}$ , showed a maximum breakdown voltage of >1.0 kV and a low differential specific on-resistance of 0.28 $\text{m}\Omega $ -cm2. Moreover, these diodes exhibited an excellent rectifying behavior with a low minimum ideality factor of 1.36 and a punch-through electric field comparable to the state-of-the-art vertical GaN-on-GaN p-n diodes grown by metalorganic chemical vapor deposition (MOCVD). These results suggest that all-MBE vertical GaN-on-GaN p-n diodes grown by NH3 MBE can be promising for small-size high-power electronic devices. [ABSTRACT FROM AUTHOR]

Photocathodes have a wide range of applications, and different materials can be used depending on the incident photon wavelength. The structure and composition of a crystalline material can strongly affect the electronic properties such as the electron affinity and the work function. Molecular beam epitaxy (MBE) provides much improved control over the composition and synthesis of a photocathode versus traditional manufacturing methods, which allows these electrical and optical properties to be optimized for a particular application. In this article, we use density functional theory (DFT) through commercially available MedeA-VASP simulation software to identify the available parameter space of electron affinity and absorption coefficient by varying the stoichiometry and crystallinity. We identify trends to motivate the manufacture of new dicesium telluride- and gallium arsenide-like materials via MBE to optimize photocathode performance for a particular application. [ABSTRACT FROM AUTHOR]

Alloying is a commonly accepted method to tailor properties of semiconductor materials for specific applications. Only a limited number of semiconductor alloys can be easily synthesized in the full composition range. Such alloys are, in general, formed of component elements that are well matched in terms of ionicity, atom size, and electronegativity. In contrast there is a broad class of potential semiconductor alloys formed of component materials with distinctly different properties. In most instances these mismatched alloys are immiscible under standard growth conditions. Here we report on the properties of GaN1-xAsx, a highly mismatched, immiscible alloy system that was successfully synthesized in the whole composition range using a nonequilibrium low temperature molecular beam epitaxy technique. The alloys are amorphous in the composition range of 0.170.2, and to the upward movement of the valence band for alloys with x

We found that nitrogen (N) and silicon (Si) were unintentionally co-doped in Ga2O3 layers grown by plasma-assisted molecular beam epitaxy (PAMBE), and that the ratio between N and Si could be controlled by O/Ga flux ratio during the growth. Note that N and Si act as a deep acceptor (theoretically predicted) and a shallow donor (experimentally confirmed) in Ga2O3, respectively. Taking advantage of this unique characteristic of PAMBE-grown Ga2O3, normally off operation of Ga2O3 metal–oxide–semiconductor field-effect transistors (MOSFETs) was demonstrated. The unintentionally-doped Ga2O3 channel layer of the MOSFETs had N and Si concentrations of $1\times 10^{18}$ and $2\times 10^{17}$ cm−3, respectively, and thus it was considered to behave as a p-type material. The MOSFETs showed a turn-on threshold gate voltage of larger than +8 V, implying formation of an inversion channel in the N-doped Ga2O3 layer. Although the ON-state drain current (${I}_{\mathrm{d}}$) remained in the subthreshold regime owing to limited gate voltage swing, the ${I}_{\mathrm{d}}$ ON/OFF ratio exceeded five orders of magnitude. [ABSTRACT FROM AUTHOR]

An enhancement-mode $\beta $ -Ga2O3 metal–oxide–semiconductor field-effect solar-blind phototransistor on Si-doped homoepitaxial film grown by molecular beam epitaxy is demonstrated in this letter. Gate-recess process was employed to fully deplete the Ga2O3 channel to achieve positive threshold voltage ${V}_{{\textsf {th}}}$ (7 V), which broadens the operating range of the solar-blind phototransistor. The dark current of about 0.7 pA is extremely low. Under 254-nm light illumination of 63 $\mu \text{W}$ /cm2, the change of drain current reaches more than 6 orders of magnitude. Record high detectivity of 1.3 $\boldsymbol {\times }\,\,10^{{\textsf {16}}}$ Jones and photo-to-dark current ratio of $1.1\,\,{\boldsymbol {\times }}\,\,10^{{\textsf {6}}}$ are obtained, respectively. In addition, the rise and decay time are as short as 100 and 30 ms, respectively. High responsivity of $3\,\,\boldsymbol {\times }\,\, 10^{{\textsf {3}}}$ A/W and external quantum efficiency of $1.5\,\,\boldsymbol {\times }\,\,10^{{\textsf {6}}}$ % are also achieved with apparent solar-blind photodetection. [ABSTRACT FROM AUTHOR]

Low-dimensional nanowires have received increased interest as building blocks for electronic and photonic devices. In this article, we review the recent progress made on III -nitridenanowire photonic devices by molecular beam epitaxy (MBE), with a focus on micro-LED s, deep-ultraviolet (UV)-light emitters, and solar fuel and artificial photosynthesis devices. The challenges and prospects of III -nitride nanowires for these applications are also discussed. [ABSTRACT FROM AUTHOR]

We study magnetic and transport properties of Co1+xFeV1−xSi epitaxial films grown by molecular beam epitaxy. Even though we co-evaporate each element with stoichiometry, Co-rich and V-poor CoFeVSi films are obtained, which results in a relatively large value of the saturation magnetic moment compared with the theoretical value. However, for the nonstoichiometric films, electrical and magnetotransport properties indicate a spin-gapless semiconductor-like electronic band structure. [ABSTRACT FROM AUTHOR]

The detection accuracy of the multibeam echo sounder (MBES) can be damaged severely and inevitably due to the mismachining tolerance of the transducer array. Therefore, it is necessary to demonstrate the performance of the multi-element transducer array to guarantee the accuracy of the processing algorithms. In this paper, a kind of multi-element MBES receiving transducer array self-calibrating method is proposed to manage the serious defocusing problem of the conventional methods. We analyze the error source and their effect on the MBES detection. The near-field beamforming and the least residual error criterion methods are employed to calibrate the average element spacing. The integrated self-calibrating method is managed to calibrate the transducer array, considering the coupling between the circuits and the element with a channel uniformity problem. An experiment is carried in a small-size tank to evaluate the method proposed. The outfield experimental data are compensated by the average element spacing and the beam response error estimated in the tank experiment. The simulations and the field data processing results indicate that the novel method proposed can effectively demonstrate the performance of the receiving transducer array and guarantee the coverage of the MBES system. [ABSTRACT FROM AUTHOR]

Ga and Sn surface-segregated GeSn (Seg. p+-GeSn) layer with an average active Ga doping concentration of $3.4 \times 10^{20}$ cm $^{-3}$ and surface Sn composition of ~7% was grown on the Ge (100) substrate by molecular beam epitaxy. An ultralow specific contact resistivity $\rho _{\textsf{c}}$ down to $4.4 \times 10^{-\textsf {10}} \,\,\Omega \cdot \text {cm}^{\textsf {2}}$ is achieved for the Ti contact on Seg. p+-GeSn film. Average $\rho _{\textsf{c}}$ , extracted from 14 sets of nano-scale transmission line method test structures and a collection of more than 90 devices, is $6.5 \times 10^{-\textsf {10}} \,\,\Omega \cdot \textsf {cm}^{\textsf {2}}$. This is the lowest $\rho _{\textsf {c}}$ for any nonlaser-annealed contacts. In addition, the benefits of Ga and Sn surface segregation on $\rho _{\textsf {c}}$ reduction were investigated. Increasing the surface Sn composition from 5% to 8% lowers $\rho _{\textsf {c}}$ from $1.4\times 10^{-\textsf {9}}$ to $1.1\times 10^{-\textsf {9}} \,\,\Omega \cdot \textsf {cm}^{\textsf {2}}$ and the Ga surface segregation further reduces $\rho _{c}$ down to $6.5\times 10^{-\textsf {10}} \,\,\Omega \cdot \textsf {cm}^{\textsf {2}}$. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate high-performance vertical solar-blind Schottky photodetectors on MBE-grown homoepitaxial (010)-oriented $\beta $ -Ga2O3 films. The structure, consisting of (100 nm) $\beta $ -Ga2O3/(60 nm) $\text{n}^{++} \beta $ -Ga2O3, was grown on a Fe-doped insulating (010) $\beta $ -Ga2O3 substrate. Ni/Au and indium were used as the Schottky and Ohmic contacts, respectively. The devices exhibited a rectification ratio of ~107 with turn-on voltage ~1 V and an ideality factor of 1.31. The extracted Schottky barrier height was 1.4 eV. The photodetectors showed low dark current of 0.3 nA at 5 V with a photo-to-dark current ratio of ~102 at 0 V. The devices exhibited a zero-bias responsivity of 4 mA/W at 254 nm corresponding to an external quantum efficiency ~3 %, with a UV-to-visible rejection ratio >103, showing true solar-blind operation. The transient response of the devices indicated rise/fall times of ~100 ms. Temperature-dependent current–voltage characteristics agree with the thermionic emission model. [ABSTRACT FROM AUTHOR]

The vacuum pocket retaining molecular beam epitaxial regrowth of the nano‐patterned GaSb surface was demonstrated. The high contrast 2D photonic crystal layer was incorporated into the test 2 µm emitting laser heterostructure. The photonic dispersion determined from angle‐resolved electroluminescence experiment showed four well‐resolved bands corresponding to the model predictions for the square lattice. The single‐mode lasing near 2 µm has been observed at the temperature corresponding to the alignment of the photonic crystal band‐edge states and the quantum well gain peak. The reference devices without the photonic crystal layer emitted trivial spectra and did not lase at any temperature. [ABSTRACT FROM AUTHOR]

The demonstration of SrSnO3 metal–semiconductor field effect transistors (MESFETs) is reported. The device layer structure consists a 28-nm-thick n-type SrSnO3 film on top of an 11-nm-thick undoped SrSnO3 film grown by hybrid molecular beam epitaxy on a (110) GdScO3 substrate. The MESFETs utilize a Pt Schottky gate electrode and diffused Sc Ohmic contacts. A Schottky barrier height of 1.55 eV was extracted for Pt on SrSnO3 using capacitance-voltage measurements. Devices with a gate length of $3~\mu \text{m}$ and source–drain spacing of 9 $\mu \text{m}$ had a drive current of 36 mA/mm at ${V} _{\textsf {GS}} = +1$ V and ${V} _{\textsf {DS}} = +3.5$ V, and a peak extrinsic (intrinsic) transconductance of 17 mS/mm (35 mS/mm). [ABSTRACT FROM AUTHOR]

GaN vertical trench-MOSFETs incorporating molecular beam epitaxy (MBE) regrown channel are developed and investigated. The channel regrowth by MBE prevents repassivation of the p-type GaN body while promising higher channel mobility. Two different designs of the lateral portion of the regrown channel are compared: without or with an n+-GaN buried layer. Without an n+ buried layer, a respectable 600-V breakdown voltage (BV) is measured in the absence of edge termination, indicating a decent critical field strength (>1.6 MV/cm) of the regrown channel. However, the ON-resistance is limited by the highly resistive lateral channel due to Mg incorporation. With an n+ buried layer, the limitation is removed. Excellent ON-current of 130 mA/mm and ON-resistivity of $6.4 ~\rm {m\Omega \cdot cm^{2}}$ are demonstrated. The BV is limited by high source–drain leakage current from the channel due to drain-induced barrier lowering (DIBL) effect. Device analysis together with TCAD simulations points out the major cause for the DIBL effect: the presence of interface charge beyond a critical value ( $\sim 6\times 10^{12}\,\,\rm {cm^{-2}}$ ) at the regrowth interface on etched sidewalls. This paper provides valuable insights into the design of GaN vertical trench-MOSFET with a regrown channel, where simultaneous achievement of low ON-resistivity and high BV is expected in devices with reduced interface charge density and improved channel design to eliminate DIBL. [ABSTRACT FROM AUTHOR]

We report on crystallographic behaviors of inclined GaAs nanowires (NWs) self-crystallized on GaAs (001) substrate. The NWs were grown on hydrogen-silsesquioxane (HSQ) covered substrates using molecular beam epitaxy (MBE). Commonly, the epitaxial growth of GaAs 111 B (B-polar) NWs is prominently observed on GaAs (001); however, we yielded a remarkable number of epitaxially grown GaAs 111 A (A-polar) NWs in addition to the majorly obtained B-polar NWs. Such NW orientations are always accompanied by a typical inclined angle of 35° from (001) plane. NWs with another inclined angle of 74° were additionally observed and attributed to be 111 -oriented, not in direct epitaxial relation with the substrate. Such 74° NWs' existence is related to first-order three-dimensional (3D) lattice rotation taking place at the very beginning of the growth. It turns out that spatially 60° lattice rotation around 111 directions at GaAs seeds is essentially in charge of A- and B-polar 74° NWs. Transmission electron microscope observations reveal a high density of twinning in the B-polar NWs and twin-free characteristic in the A-polar NWs. [ABSTRACT FROM AUTHOR]

Although selective dry etches exist for GaN, it is difficult to selectively etch AlN in heterostructures with other conventional III-N epitaxial materials. The reduction in etch rate resulting from the addition of 2%–16% scandium to ScxAl1–xN in conventional Cl2/BCl3/Ar inductively coupled plasma etching is presented. Smooth, epitaxial ScxAl1–xN layers are grown by RF-plasma-assisted molecular beam epitaxy directly on 4H-SiC substrates. The etch selectivity with respect to AlN is as high as 10.6 and 11.2 for x~\boldsymbol =0.02 and 0.16, respectively, allowing ScxAl1–xN to act as an etch-stop layer with minimal misfit strain when grown within either AlN or GaN based heterostructures. [ABSTRACT FROM AUTHOR]

The quality of epitaxial layers in quantum cascade lasers (QCLs) has a primary impact on QCL performance, and establishing correlations between epitaxial growth and materials properties is of critical importance for continuing improvements. We present an overview of the growth challenges of these complex QCL structures; describe the metalorganic vapor phase epitaxy growth of AlInAs/GaInAs/InP QCL materials; discuss materials properties that impact QCL performance; and investigate various QCL structure modifications and their effects on QCL performance. We demonstrate uncoated buried-heterostructure 9.3-μm QCLs with 1.32-W continuous-wave output power and maximum wall plug efficiency (WPE) of 6.8%. This WPE is more than 50% greater than previously reported WPEs for unstrained QCLs emitting at 8.9 μm and only 30% below strained QCLs emitting around 9.2 μm. [ABSTRACT FROM PUBLISHER]

We demonstrate high-performance mid-wavelength p - i - n infrared detectors based on InAs/GaSb type-II superlattices (SLs) grown by a production-scale metalorganic chemical vapor deposition system. Through a specially-designed gas switching sequence and the use of GaAs-type of interfacial layers, strain-balanced SLs with excellent material quality were obtained, as evidenced by atomic force microscopy, photoluminescence, X-ray diffraction, and transmission electron microscopy. The processed devices, with a cutoff wavelength around 4.8 , exhibited a R0A of 2.3\times 10^{4}~\Omega cm2 and a peak responsivity of 1.4 A/W at 77 K. A specific detectivity of 7.2\times 10^{12} cmHz ^1/2 /W was achieved at 3.7~\mu \textm . These values are comparable with those reported for InAs/GaSb SL detectors with similar cutoff wavelengths grown by molecular beam epitaxy. [ABSTRACT FROM PUBLISHER]

The tunnel-FET (TFET) is a promising candidate for future low-power logic applications, because it enables a sub-60-mV/decadesubthresholdswing. However, themost experimental TFETs are plagued by unwanted trap-assisted tunneling (TAT) and Shockley–Read–Hall (SRH) carrier generation, which degrade the swing and increase the leakage floor, hence forming a major roadblock for TFET adoption. This degradation is attributed to bulk traps, semiconductor/oxideinterface traps, and/or heterojunction interface traps, but it is still unclear which of the three trap types are dominant. In this paper, we focus on TAT and SRH caused by bulk traps. We calibrate SRH and TAT models with the help of In0.53Ga0.47As p+/n+ and p+/i/n+ diodes grown on lattice matched substrates by molecular beam epitaxy (MBE). We then perform calibrated simulations of an In0.53Ga0.47As TFET, which show bulk SRH and TAT are sufficiently low compared with the target OFF-state current and, hence, not a significant issue. Therefore, it is likely that high SRH and TAT commonly observed in experimental homojunction InGaAs TFETs, MBE-grown on lattice matched substrates, are not caused by bulk semiconductor defects, but by semiconductor/oxide interface defects. [ABSTRACT FROM PUBLISHER]

High-voltage vertical regrown p-n junction diodes on bulk GaN substrates are reported in this letter with molecular-beam-epitaxy regrown p-GaN on metalorganic-chemical-vapor-deposition grown n-GaN drift region. The highest breakdown voltage is measured at 1135 V, and the differential on-resistance is 3.9 mOhm.cm2 at room temperature. The forward I–V show a turn-ON voltage near 3.9 V and an ideality factor of 2.5. Electroluminescence measurement of regrown p-n junctions shows ~30 times reduced emission intensity compared with as-grown p-n junctions, indicating presence of excessive non-radiative recombination centers introduced by the regrowth process. Temperature dependent reverse I–V measurements suggest that variable range hopping inside the depleted regrown p-GaN layer is likely the mechanism of the reverse leakage. This is the first high-voltage vertical regrown p-n junction ever reported in the GaN system. [ABSTRACT FROM AUTHOR]

Research on nanowire growth with patterned arrays of catalyst has shown that wire-to-wire spacing is an important factor affecting nanowire quality. To improve the process yield and the length uniformity of fabricated nanowires, it is important to reduce the resource competition between nanowires during the growth process. In this paper, we propose a physical-statistical nanowire-interaction model considering the shadowing effect and shared substrate diffusion area to determine the optimal pitch that would ensure the minimum competition between nanowires. A sigmoid function is used in the model, and the method of least squares is used to estimate the model parameters. The estimated model is then used to determine the optimal spatial arrangement of catalyst arrays. This work is an early attempt at the physical-statistical modeling of selective nanowire growth for the improvement of process yield. [ABSTRACT FROM AUTHOR]

In this paper, germanium–bismuth (Ge1–xBix, x = 0 –0.32) is grown by low-temperature molecular beam epitaxy. Because Bi is an element belonging to group V, GeBi films show inherent n-type doping properties compared with GeSn ones. Inherent n-type Ge1–xBix films with a doping concentration of 2 \times 10^{15} – 2 \times 10^{16} /cm3 are epitaxially deposited on p-type Si substrates to form p-n junctions. Current–voltage measurements show that the dark current density of the diodes can approach 0.32 A/cm2. The influence of Bi concentration on the infrared (IR) and terahertz (THz) transmittance of the films is investigated. Near-IR (1–2 \mu \textm ) and mid/far-IR (2.6–10 \mu \textm ) responsivities of the films are 0.65 and 0.032 A/W, respectively. The THz wave transmittance is tuned by ~6%–8% by tailoring the bias voltage. A modulation depth of ~12% is obtained for a Ge0.78Bi0.22/p-Si diode. The dynamic modulation characteristics of n-Ge1–xBix/p-Si diodes are further investigated using a 340-GHz carrier. The experimental maximum THz wave modulation speed is up to 2 MHz. The present results demonstrate that n-GeBi/p-Si diodes are promising for both mid/far-IR photodetectors and broadband high-speed THz wave modulators. [ABSTRACT FROM AUTHOR]

For the development of GaN-based ultraviolet (UV) photodetectors, a simple epilayer structure consisting of GaN (600 nm)/AlN (200 nm) was grown on 100-mm Si substrate using ammonia-molecular beam epitaxy growth technique. The epilayers were crack-free and showed good surface and optical quality. Metal–semiconductor–metal (MSM) interdigitated Schottky-based contacts, fabricated using Ni/Au metallic layers, showed a low dark current of 0.43 nA at 15 V. The analysis of dark current as a function of applied bias revealed that the major current conduction mechanism was through thermionic emission over a Schottky barrier of 0.902 eV. Moreover, the Schottky barrier was found to reduce with the bias, which has been attributed to the image force reduction in the devices. The MSM devices exhibited a peak responsivity of 0.183 A/W at an incident wavelength of 362 nm with a UV/visible rejection ratio of 170. The peak responsivity corresponds to external quantum efficiency of ~70%. The devices also showed good linearity and almost flat responsivity with input power for the applied bias beyond 7 V. [ABSTRACT FROM PUBLISHER]

Due to the difficulty of GaN epitaxy growth on Si(001) substrate, GaN-on-Si wafers are generally grown on Si(111) substrates. Because of the poor electrical characteristics of Si(111) orientation, monolithic integration between CMOS ICs and GaN devices cannot be implemented on GaN-on-Si(111) wafers. At this point of view, Si(110) substrate will be an alternative choice for GaN-on-Si epitaxy growth, because it has good atomic arrangement with AlN seed layer and an advantage of excellent hole mobility characteristics over Si(001). We have developed high quality GaN epitaxy growth technique on Si(110) substrate using NH3 MBE and demonstrated normally-off AlGaN/GaN-on-Si(110) metal–oxide–semiconductor-heterojunction field-effect transistors with an OFF-state breakdown voltage of 610 V. The fabricated device exhibited promising characteristics comparable with those achieved on conventional GaN-on-Si(111) wafers. [ABSTRACT FROM PUBLISHER]

The (Nd1–xGdx)2O3 thin films were grown on Si(001) in 2005 using molecular beam epitaxy followed by an in vacuo metallization of Pt contacts. Pt/(Nd1–xGdx)2O3/Si(001) metal-oxide-semiconductor structures have been characterized several times over the period of 2005–2015 in order to investigate the stability of their physical and electrical properties. Core-level X-ray photoelectron spectroscopy (XPS) spectra remeasured during 2015 depict that the layer still retains its original properties that were measured in 2005. Although there has been some degradation of electrical properties such as capacitance and leakage current over several years, interestingly the midgap density of interface traps’ ( $D_{{\mathrm{it}}}) value has been found to be decreased from 1.1 \times 10^12 to 3.5 \times 10^11 eV ^-1 cm ^-2 over the years. The formation of silicate-like interface inferred from XPS measurements can be attributed to such an improvement over this period. Time-dependent dielectric breakdown measurements under constant current stress and constant voltage stress were also carried out to investigate the reliability of the structure. [ABSTRACT FROM PUBLISHER]