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This paper presents a theoretical analysis of an nBp infrared barrier detector's performance intended to operate at a room temperature (300 K) based on AIIIBV materials—In1-xGaxAsySb1−y quaternary compound—lattice-matched to the GaSb substrate with a p-n heterojunction ternary Al1−xGaxSb barrier. Numerical simulations were performed using a commercial Crosslight Software—package APSYS. The band structure of the nBp detector and the electric field distribution for the p-n heterojunction with and without a potential barrier were determined. The influence of the barrier-doping level on the detector parameters was analyzed. It was shown that Shockley-Read-Hall (SRH) recombination plays a decisive role in carrier transport for lifetimes shorter than 100 ns. The influence of the absorber/barrier thickness on the detector's dark current density and photocurrent was investigated. It was shown that valence band offset does not influence the device's performance. The quantum efficiency reaches its maximum value for an absorber's thickness of ~3 μm. The performed simulations confirmed the possibility of the detector's fabrication exhibiting high performance at room temperature based on quaternary compounds of AIIIBV materials for the short wavelength infrared range. [ABSTRACT FROM AUTHOR]

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High-voltage gradual p0–i–n0 junctions of AlxGa1 –xAs1 –ySby with x ~ 0.24 and y ~ 0.05 in the i‑region were studied using capacitance-voltage characteristics method and transient spectroscopy of deep levels. It has been established that the effective recombination trap in them is the DX-center of the Si donor impurity, with a thermal activation energy Et = 414 meV, a capture cross section σn = 1.04 × 10–14 cm2, and a concentration Nd = 2.4 × 1015 cm–3. In the heterostructures studied, there were no deep levels associated with dislocations. [ABSTRACT FROM AUTHOR]

Thermophotovoltaic conversion using heat to generate electricity in photovoltaic cells based on the detraction of thermal radiation suffers from many engineering challenges. The focus of this paper is to study the nanostructure of AlGaAsSb for thermophotovoltaic energy conversion using lattice-matched heterostructures of GaSb-based materials in order to overcome the current challenges. The XAFS spectroscopy technique was used to analyze electronic structures and optical properties of GaSb, (Al, In) GaSbAs. The XAFS spectroscopy analysis showed a powerful decay at peak intensity that reveals to be related to a loss in Sb amount and light As atoms replaced in Sb atoms by 25%. Moreover, it was found that Al/In doped samples have highly symmetric data features (same atomic species substitution). The narrow direct bandgap energy, Eg of Al0.125Ga0.875Sb0.75As0.25 material raised (0.4–0.6 eV) compared to conventional photovoltaic cell bandgap energy (which is generally less than 0.4 eV) with weak absorption coefficients. The thermoelectric properties of AlGaAsSb computed via Botlztrap code showed that the electrons made up the majority of the charge carriers in AlGaAsSb. This nanostructure material exhibited a higher and acceptable figure of merit and demonstrated a promising thermoelectric material for solar thermophotovoltaic applications. [ABSTRACT FROM AUTHOR]

We provide an overview of our progress on the development of linear mode avalanche photodiodes (LmAPDs) on InP substrates using antimony (Sb)-based multipliers for short-wavelength infrared (SWIR) spectral region. We identify the key figures of merit of LmAPDs to provide higher sensitivity and speed for applications like light detection and ranging (LiDAR) and remote sensing. We discuss the design of separate absorption, charge, and multiplication (SACM) APDs that are used for narrow gap absorption. We summarize our results on the impact ionization, multiplication gain, dark current, and excess noise of AlGaAsSb and AlInAsSb multipliers lattice-matched to InP substrates. Finally, we identify the key technical challenges associated with the development of SACM APDs on InP substrates. [ABSTRACT FROM AUTHOR]

Digital alloy and random alloy Al0.85Ga0.15As0.56 Sb0.44 avalanche photodiodes (APDs) exhibit low excess noise, comparable to Si APDs. Consequently, this material is a promising multiplication layer candidate for separate absorption, charge, and multiplication structure APDs with high gain-bandwidth product. Characterization of the impact ionization coefficients of electrons (α) and holes (β) plays an important role in the simulation of avalanche photodiodes. The multiplication gain curves of eight p+-i-n+ and n+-i-p+ APDs covering a wide range of avalanche widths have been used to determine the electric field dependence of the impact ionization coefficients of Al0.85Ga0.15As0.56Sb0.44. A large impact ionization coefficient ratio between that of electrons to holes was seen across a wide electric field range. Simulations of the avalanche multiplication in these structures using a random path length (RPL) model gave good agreement with experimental results over almost three orders of magnitude, and a mixed injection method was employed to verify the extracted impact ionization coefficients. Interestingly, no difference in the impact ionization coefficients was seen between digital alloy and random alloy Al0.85Ga0.15As0.56Sb0.44. This knowledge of impact ionization coefficients is beneficial for the future utilization of the AlxGa1-xAsySb1-y material system. [ABSTRACT FROM AUTHOR]

Avalanche photodiodes (APDs) made with the material AlGaAsSb (lattice-matched to InP) exhibit very low excess noise characteristics. We demonstrate a Separate Absorption and Multiplication APD (SAM-APD) incorporating a GaAs0.52Sb0.48 (GaAsSb) absorption region and an Al0.85Ga0.15As0.56Sb0.44 (AlGaAsSb) avalanche region. Our GaAsSb/AlGaAsSb SAM-APD exhibits a cut-off wavelength of 1.70 μm at room temperature and a responsivity of 0.39 A/W at 1.55 μm wavelength (with no antireflection coating). Temperature dependence of the breakdown voltage was obtained from avalanche gain data from multiple devices operated at 77 to 295 K. This produced a temperature coefficient of breakdown voltage of 4.31±0.33 mV/K, a factor of 10 and 5 smaller than values for comparable InP and InAlAs SAM-APDs. The very small temperature coefficient of this work is consistent with the extremely weak temperature dependence of avalanche breakdown previously observed in AlGaAsSb diodes. [ABSTRACT FROM AUTHOR]

Thermophotovoltaic conversion using heat to generate electricity in photovoltaic cells based on the detraction of thermal radiation suffers from many engineering challenges. The focus of this paper is to study the nanostructure of AlGaAsSb for thermophotovoltaic energy conversion using lattice-matched heterostructures of GaSb-based materials in order to overcome the current challenges. The XAFS spectroscopy technique was used to analyze electronic structures and optical properties of GaSb, (Al, In) GaSbAs. The XAFS spectroscopy analysis showed a powerful decay at peak intensity that reveals to be related to a loss in Sb amount and light As atoms replaced in Sb atoms by 25%. Moreover, it was found that Al/In doped samples have highly symmetric data features (same atomic species substitution). The narrow direct bandgap energy, Eg of Al0.125Ga0.875Sb0.75As0.25 material raised (0.4–0.6 eV) compared to conventional photovoltaic cell bandgap energy (which is generally less than 0.4 eV) with weak absorption coefficients. The thermoelectric properties of AlGaAsSb computed via Botlztrap code showed that the electrons made up the majority of the charge carriers in AlGaAsSb. This nanostructure material exhibited a higher and acceptable figure of merit and demonstrated a promising thermoelectric material for solar thermophotovoltaic applications.

The electrical and optical properties of non-doped and Te doped 6.5 periods AlGaAsSb/AlAsSb Bragg mirrors on InP grown by MBE with different types of interfaces between ternary and quaternary layers are reported. The techniques employed were photoluminescence, refectivity and IxV measurements. The digital alloy gradient interface seems to be the best alternative to optimize conduction without significant refectivity losses.

Avalanche breakdown characteristics are essential for designing avalanche photodiodes. In this letter, we investigated the effects of adding Ga to Al1–xGaxAs0.56Sb0.44 quaternary alloys. Using p-i-n diodes with a 100-nm i—region and alloy composition ranging from $x=0$ to 0.15, we found that the bandgap energy of Al1–xGaxAs0.56Sb0.44 reduces from 1.64 to 1.56 eV. The corresponding avalanche breakdown voltage decreases from 13.02 to 12.05 V, giving a reduction of 64.7 mV for every percent addition of Ga. The surface leakage current was also found to be significantly lower in the diodes with $x=0.10$ and 0.15 suggesting that Ga can be added to reduce the surface leakage current while still preserving the lattice match to InP substrate. The data from this letter can be downloaded freely. [ABSTRACT FROM PUBLISHER]

The reflectivity of a Bragg mirror composed by materials of the antimony family (AlGaAsSb/AlAsSb), doped with tellurium, is analyzed in this work. The sample was prepared by molecular beam epitaxy (MBE) and the reflectivity was measured by Fourier Transform Infra-Red Spectroscopy (FTIR). In order to discuss the Bragg mirror properties, the experimental reflectivity is compared to a simulation of the reflectivity based on the matrix formalism.

São apresentadas as propriedades elétricas e ópticas de espelhos de Bragg com 6.5 períodos de AlGaAsSb/ AlAsSb não dopado e dopados com Te, sobre InP, crescidos por MBE com diferentes tipos de interface entre as camadas de material ternário e quaternário. As técnicas empregadas foram fotoluminescência, reflectividade e medições de IxV. A interface com liga digital em gradiente parece ser a melhor alternativa para otimizar condução elétrica sem perdas significativas da reflectividade.

The antimonide laser heterostructures growth technology using MBE epitaxy is currently well-developed, while MOVPE method is still being improved. It is known that the principal problem for MOVPE is the oxygen and carbon contamination of aluminium containing waveguides and claddings. The solution would be to apply a proper aluminium precursor. In this study we present the results of metal-organic epitaxy of In- and Al-containing layers and quantum well structures composing antimonide lasers devices. Special emphasis was put on the aluminium precursor and its relation to AlGaSb and AlGaAsSb materials properties. The crystalline quality of the layers grown with two different Al precursors was compared, very good structural quality films were obtained. The results suggested a substantial influence of precursors pre-reactions on the epitaxial process. The oxygen contamination was measured by SIMS, which confirmed its dependence on the precursor choice. We also optimised the GaSb substrate thermal treatment to deposit high quality GaSb homoepitaxial layers. Quaternary InGaAsSb layers were obtained even within the predicted miscibility gap, when arsenic content reached high above 10% values. InGa(As)Sb/AlGa(As)Sb quantum wells were grown and their optical properties were characterised by photoluminescence and photoreflectance spectroscopy. Type-I quantum wells showed a fundamental optical transition in the 1.9-2.1 μm range at room temperature. The epitaxial technology of the structures was subjected to an optimisation procedure. The investigated layers and heterostructures can be considered for application in laser devices. [ABSTRACT FROM AUTHOR]

Analisamos neste trabalho, a refletividade de um espelho de Bragg composto por materiais da família do antimônio (AlGaAsSb/AlAsSb) dopado com telúrio. As amostras foram preparadas através da técnica de epitaxia por feixe molecular MBE (Molecular Beam Epitaxy) e as medidas de refletividade pela técnica de espectroscopia de infravermelho por transformada de Fourier FTIR (Fourier Transform Infra- Red). Para discussão das propriedades do espelho de Bragg comparamos a refletividade obtida experimentalmente e uma simulação baseada no formalismo matricial.

We present a theoretical analysis of type-II heterostructures based on the AlInAs/AlGaInAs/AlGaAsSb material system. The band structure is modelled using a 6×6 k · p Hamiltonian that accounts for valence band mixing and strain effects. Design maps are produced and a comparison of possible design routes is made in terms of band structure. [Copyright &y& Elsevier]

GaInAsSb and AlGaAsSb alloys have been grown by organometallic vapor phase epitaxy (OMVPE) using all organometallic sources, which include tritertiarybutylaluminum, triethylgallium, trimethylindium, tertiarybutylarsine (TBAs), and trimethylantimony. Excellent control of lattice-matching both alloys to GaSb substrates is achieved with TBAs. GaInAsSb/AlGaAsSb multiple quantum well (MQW) structures grown by OMVPE exhibit strong 4K photoluminescence with full width at half maximum of 10 meV, which is comparable to values reported for quantum well (QW) structures grown by molecular beam epitaxy. Furthermore, we have grown GaInAsSb/AlGaAsSb MQW diode lasers which consist of n- and p-doped Al0.59Ga0.41As0.05Sb0.95 cladding layers, Al0.28Ga0.72As0.02Sb0.98 confining layers, and four 15 nm thick Ga0.87In0.13As0.12Sb0.88 quantum wells with 20 nm thick Al0.28Ga0.72As0.02Sb0.98 barrier layers. These lasers, emitting at 2.1 µm, have exhibited room-temperature pulsed threshold current densities as low as 1.2 kA/cm2. [ABSTRACT FROM AUTHOR]

We report the molecular beam epitaxial growth of AlGaAsSb (0.0 ≤ x ≤ 1.0) on undoped, liquid-encapsulated Czochralski, (100) oriented InAs substrates. The degree of lattice mismatch was determined by x-ray diffraction. The lattice matched materials ( y ≈ 0.08 + 0.08 x) were characterized by low temperature photoluminescence, electro-reflectance, and capacitance-voltage measurements. The experimental bandgap energies agree with earlier experimental results for AlGaSb, and also with a self-consistent first principles pseudopotential model. The capacitance-voltage measurements indicate background acceptor concentrations for the unintentionally-doped epitaxial layers of about 2 × 10 cm at x = 1.0 to 5 × 10 cm at x ≈ 0.0. [ABSTRACT FROM AUTHOR]

A type-II AlInP/AlGaAsSb/InP double heterojunction bipolar transistor (DHBT) with composition-graded Al content in the base is designed and grown by molecular beam epitaxy. Compared with composition-graded GaAsSb and InGaAsSb bases in DHBT, the graded AlGaAsSb base can generate a larger built-in electric field, thus reducing base transit time and improving device speed. We have fabricated AlGaAsSb graded base DHBTs and demonstrated fT/fMAX = \450/510\ \GHz for a \0.3 \times \2\ \mu\m^2 device. [ABSTRACT FROM PUBLISHER]

High-power high-brightness 1.93-μm wavelength (AlGaIn)(AsSb) tapered diode lasers with a narrow vertical waveguide design are reported for the first time. A nearly diffraction-limited continuous-wave output power of 1.5 W together with a remarkable low fast axis divergence of 43° full-width at half-maximum have been demonstrated. The maximum brightness amounts to 32 MW/cm2sr. [ABSTRACT FROM PUBLISHER]

In this letter, the authors demonstrate a wavelength flexible platform for the production of long-wavelength vertical-cavity surface-emitting lasers which provide full wavelength coverage from 1.3-1.6 μm. All-epitaxial InP-based devices with AsSb-based distributed Bragg reflectors were achieved through a common design, process, and growth technology at both the important telecommunications wavelengths of 1.3 and 1.5 μm. Thin selectively etched tunnel junctions were implemented as low-loss apertures and offer scalability to small device dimensions. Devices showed low threshold currents (<2 mA), near single-mode (SMSR>20 dB) operation, and high differential efficiency (>40% at 1.3 μm and >25% at 1.5 μm). [ABSTRACT FROM PUBLISHER]

The increasing number of subcells in multi-junction structures imposes the use of narrow bandgaps for a full harvesting of the solar spectrum. In this context, gallium antimonide (GaSb) and its lattice-matched alloys offer a great potential. To date, GaSb-based multi-junction solar cells exhibit experimental results below theoretical expectations, due to a limiting GaSb subcell. In this paper, a new design of GaSb cells comprising an Al 0.50 Ga 0.50 As 0.04 Sb 0.96 window layer is studied. With this design, an excellent conversion efficiency of 7.2% is achieved under 1 sun (AM1.5G) illumination. This performance is attributed to a significant improvement in short-circuit current. [ABSTRACT FROM AUTHOR]