Quaternary Semiconductor Alloys Research Articles

Response of mechanical and optoelectronic properties for InPxAsySb1–x–y/InAs system to composition

The compositional dependence of optical, mechanical, thermal properties, and lattice vibrations of InPxAsySb1–x–y quaternary semiconductor alloys lattice-matched to InAs substrate has been studied. In this study, the physical properties of the binary elements InAs, InSb, and InP that make up the quaternary alloy were employed. Under the virtual crystal approximation (VCA), the empirical pseudo-potential model (EPM) was used to carry out the research. Our findings are in good agreement with the available experimental and theoretical values. In the literature, the composition effect on the optical, mechanical and thermal properties of the InPxAsySb1–x–y/InAs system has not been thoroughly investigated. As a result, we focused on these properties as a function of composition.

Study of structural and electrical properties of Al-Si-In-Sn quaternary semiconductor alloy

In the present work, we have investigated the structural and electrical properties of two quaternary semiconductor alloy viz. Al62Si12In6Sn20 (ASIS-1) and Al58Si16In6Sn20 (ASIS-2) fabricated through powder metallurgy technique in our laboratory. Thin powders of Al, Si, In, and Sn metals is carefully weighted by analytical weight balance and then used to obtain homogeneous powder mixtures to construct aforementioned quaternary semiconductor alloy. A mixed powder is compacted by a compressive testing machine (CTM) at a pressure of 800 MPa to achieve green compact. The hybrid phase sintering process is carried out at 500℃ temperature at isothermal holding time about 120 min in the steel furnace (i.e. muffle furnace). The obtained samples are than characterized by optical microscopy, electrical resistivity, density, UV–VIS spectroscopy and Hall effect measurements. The density of both samples is found by 3.01 gm/cm3 and 2.96 gm/cm3, respectively. From the overall study, it is concluded that the electrical resistivity of aforesaid alloy increases with increasing the silicon percentage.

Application of Schrödinger equation in quantum well of Cu2ZnSnS4 quaternary semiconductor alloy

An approximate solution of the radial Schrödinger equation is obtained with a generalized group of potentials in the presence of both magnetic field and potential effect using supersymmetric quantum mechanics and shape invariance methodology. The energy bandgap of the generalized group of potentials was calculated for s−wave cases at the ground state. By varying the numerical values of the potential strengths, the energy band gap of Hellmann's potential and Coulomb-Hulthẻn potential respectively were obtained. It is noted that the inclusion of the potential effect greatly affects the accuracy of the results. Our calculated results are in agreement and better than the existing calculated results. The present results approximately coincide with the standard bandgap of Cu2ZnSnS4 (CZTS).

First principle investigations of structural and optoelectronic features of cubic CdxZn1−xSyTe1-y quaternary semiconductor alloys

In case of technologically important CdxZn1−xSyTe1−y quaternary alloys, structural and optoelectronic properties have been calculated for the first time with DFT based FP-LAPW approach. The PBE-GGA functional for structural properties and mainly the mBJ functional for optoelectronic properties are employed to calculate respective exchange-correlation potentials. Each specimen within CdxZn1−xSyTe1−y quaternary system is a direct band gap (Γ-Γ) semiconductor. The lattice constant reduces, while bulk modulus and band gap enhances nonlinearly with increasing anionic (S) concentration y at each cationic (Cd) concentration x. On the other hand, nonlinear increase in lattice constant, but decrease in bulk modulus and band gap is observed with increase in cationic concentration x at each anionic concentration y. Calculated contour maps for lattice constants and energy band gaps would be useful in fabricating new ternary or quaternary alloys with preferred optoelectronic features. Optical properties of the said specimens within CdxZn1−xSyTe1−y quaternary system show several interesting features. The composition dependence of each calculated zero-frequency limit shows opposite trend, while each calculated critical point shows similar trend of composition dependence of band gap. Moreover, calculations suggest the possibilities of growth of several zinc-blende (B3) CdxZn1−xSyTe1−y quaternary specimens on ZnTe, InP and GaAs substrates.

First principles investigations of structural and optoelectronic properties of cubic MgxZn1−xSeyTe1−y quaternary semiconductor alloys using FP-LAPW approach

Structural and optoelectronic properties of technologically important MgxZn1−xSeyTe1−y quaternary alloys are calculated employing DFT-based FP-LAPW approach. Computations of exchange–correlation potentials are performed with PBE-GGA for structural properties and both the mBJ and EV-GGA for optoelectronic properties. Each specimen within MgxZn1−xSeyTe1−y system is a direct band gap (Γ–Γ) semiconductor. At each cationic (Mg) concentration x, lattice constant decreases, while bulk modulus and band gap increase nonlinearly with increase in anionic (Se) concentration y. Again, nonlinear increase in lattice constant and band gap, while decrease in bulk modulus is observed with increase in cationic concentration x at each anionic concentrations y. Calculated band gap bowing for few ternary alloy systems are in good agreement with corresponding experimental data. The calculated contour maps for lattice constants and energy band gaps would be very useful for designing new quaternary alloys with desired optoelectronic properties. Optical properties of the said specimens within MgxZn1−xSeyTe1−y quaternary system show several interesting features. Composition dependence of each calculated zero-frequency limit shows opposite trend, while each calculated critical point shows similar trend of composition dependence of band gap. Finally, suitability of ZnTe and InAs as substrates for the growth of several zinc-blende MgxZn1−xSeyTe1−yquaternary alloys has been investigated.

Hylleraas potential quantum well in Cu2ZnSnS4 quaternary semiconductor alloy in the presence of magnetic field

The behavior of Cu2ZnSnS4 quantum well confined in the modified Hylleraas potential has been examined within the framework of the Nikiforov-Uvarov method for solving the radial part of the Schrödinger wave equation. The energy levels, are numerically calculated with an applied magnetic field in order to show their influence on the band gap energy Our results show that the band gap energy is significantly dependent on the applied magnetic field as well as parameters of the confining potential.

Mg induced compositional change in InGaN alloys

Tunnel junctions are indispensable elements of multi-junction solar cells. The fabrication of InGaN tunnel junctions requires the growth of degenerately doped n- and p-type layers. While highly doped n-type InGaN films have been demonstrated, the growth of degenerately p-doped InGaN films and the fabrication of high indium fraction InGaN tunnel junctions is still to be demonstrated. We present an investigation of the effect of Mg doping on the InGaN crystal properties over a large range of Mg fluxes and InN mole fractions in the range from 30% to 40%, using multiple characterization techniques. InGaN thin films were grown on GaN/sapphire templates and doped with Mg using plasma-assisted molecular beam epitaxy (PAMBE). We have found that the Mg concentration in the film increases linearly with the Mg beam equivalent pressure (BEP) at first, followed by a saturation at ∼4 × 1021 cm−3 similar to the Mg doping behavior reported for GaN. The growth rate of the alloy changes by more than 50% with the changes in the surface availability of Mg. These effects can be explained through the saturation of the atomic sites available for incorporation in the case of Mg concentration saturation and by the passivation of the free nitrogen radicals in the case of the growth rate variation. The incorporation of In and Ga depends on the flux ratio (ΦIn + ΦGa)/(ΦMg) at the growth surface and it is shown that the decrease of this ratio below a threshold of ∼2000 causes the almost complete loss of In and the formation of a new quaternary wide band gap semiconductor alloy (InGaMg)N.

CdZnSSe Thin Film for Photovoltaic Device

II-VI group quaternary semiconductor alloy thin films of cadmium zinc sulfoselenide (CdZnSSe) were prepared by chemical bath deposition technique on glass substrates. The deposition was carried out with various optimized deposition parameters such as concentration of precursor ions, deposition temperature, time, pH, etc. In order to obtain homogeneous thin films, triethanolamine (TEA) was used as complexing agent. A common cationic surfactant, cetyl-trimethylammoniumbromide (CTAB) was used as a capping agent. The as-deposited thin films were annealed at different temperatures (i.e. 100°, 300° and 500°C) and their structural and optical properties have been investigated by XRD, SEM, EDS and UV- visible optical absorption studies. The optical band gap energy was found to decrease from 2.21 to 2.01 eV, with increase in annealing temperature exhibiting a red shift.

DLTFS Investigation of Ingaasn/Gaas Tandem Solar Cell

Abstract In this paper authors present the results of identification of emission and capture processes in tandem solar cell structures based on quaternary InGaAsN semiconductor alloys by DLTFS (Deep Level Transient Fourier Spectroscopy) and by ana- lytical evaluation processes. The energies of five trap levels ET1=0.77 eV, ET2=0.47 eV, ET3=0.64 eV, HT1=0.62 eV and HT2=0.53 eV were identified with reliable accuracy. These values were obtained by available analytical procedures, verified by simulations and confirmed by reference structures with basic layer types and compared with possible reference trap data. Native structural defects in GaAs were stated as the origin of these deep energy levels

Optical method of estimation of degree of atomic ordering within quaternary semiconductor alloys

It is well known that within metal-organic vapor-phase epitaxy grown semiconductor ternary alloys atomically ordered regions are spontaneously formed during the epitaxial growth. This ordering leads to bandgap reduction and to valence bands splitting, and therefore to anisotropy of the photoluminescence emission polarization. The same phenomenon occurs within quaternary semiconductor alloys. While the ordering in ternary alloys is widely studied, for quaternaries there have been only a few detailed experimental studies of it, probably because of the absence of appropriate methods of its detection. Here, we propose an optical method to reveal atomic ordering within quaternary alloys by measuring the photoluminescence (PL) emission polarization. The measured and calculated angular dependencies of the polarized PL emission intensity from (100) surface for two semiconductor alloys: Ga0.51In0.49P and (Al0.3Ga0.7)0.5In0.5P are compared in order to estimate the degree of atomic ordering within these alloys. The method shows that the quaternary (Al0.3Ga0.7)0.5In0.5P alloy is a highly ordered structure with the value of the atomic ordering degree close to 0.5.

Structural and Optical Properties of GaAs0.5Sb0.5 and In0.5Ga0.5As0.5Sb0.5: ab initio Calculations for Pure and Doped Materials

We perform a first-principles study to evaluate the structural, electronic and optical properties of GaAsxSb1−x ternary and InyGa1−yAsxSb1−x quaternary semiconductor alloys up to x = 0.5, y = 0.5. We employ the Perdew-Burke-Ernzerhof form of the generalized gradient approximation (GGA) within the framework of density functional theory (DFT) by using a simulation program. Calculations are carried out in different configurations. For these alloys, lattice parameters and optical band gap energy are calculated. The optical band gaps vary with increasing and decreasing As and In concentrations, respectively. The optical conductivity, absorption and the real part of the dielectric function ∊1(ω) are discussed. Our results agree well with the theoretical and experimental data available in the literature.

Structural and electronic properties of Ga1−xInx As1−yNy quaternary semiconductor alloy on GaAs substrate

We have presented structural and electronic properties of binary (GaAs, GaN and InAs), ternary (Ga1−xInxAs and GaAs1−yNy) and quaternary (Ga1−xInxAs1−yNy) semiconductor alloys by using a first-principles pseudopotential technique. The structural and electronic properties of Zinc-Blende phase of these materials have been calculated by using the local density approximation (LDA) of the density-functional theory (DFT). To obtain the lattice parameter and band gap energy of the (GaInAsN) quaternary semiconductor alloy we separately calculated the lattice constant and band gap energies of ternary semiconductor alloys, namely GaAsN and GaInAs. The calculated lattice constant, bulk modulus and the direct band gaps for studied semiconductors showed great parallelism with the previous available theoretical and experimental studies.

A TEM Microstuctural Study of the Factors Affecting the Compositional Modulation in GaInAsSb/GaSb Films

Quaternary semiconductor alloys based on GaSb are suitable for thermo-photo voltaic cell applications as they have low and adjustable band-gap. However, they exhibit phase separation which destroys band-gap uniformity. In this work, GalnAsSb thin films grown on GaSb vicinal substrates were studied by Transmission Electron Microscopy, in order to determine the influence of the growth parameters on phase separation. It was found that the coatings exhibit two types of compositional modulation, one parallel and the other forming an angle with the substrate plane.

Elastic properties of AlxIn1−xPySb1−y and AlxGa1−xPySb1−y lattice matched to InAs substrate

The elastic constants and related properties of zinc-blende AlxIn1−xPySb1−y and AlxGa1−xPySb1−y quaternary semiconductor alloys lattice matched to InAs substrate are obtained for various aluminium concentrations over the range 0–1 using the pseudopotential method within the virtual crystal approximation combined with the Harrison bond–orbital model. The agreement between our results and published experimental data, which are only available for binary parent compounds, is generally satisfactory, while our calculated results for quaternaries of interest are predictions. Except for the internal strain parameter, all studied quantities are found to exhibit the same qualitative behavior with respect to the composition x when replacing the indium (In) by the gallium (Ga). The numerically calculated results provide more opportunities to obtain diverse elastic properties while still controlling the composition components.

Band gaps of the dilute quaternary alloys GaNxAs1−x−yBiy and Ga1−yInyNxAs1−x

We report strong band gap photoluminescence at room temperature in dilute quaternary GaNxAs1−x−yBiy alloys (x<1.6%,y<2.6%) grown by molecular beam epitaxy. The band gap of the alloy can be approximated by the band gap of GaAs minus the reduction in gap associated with the effects of N and Bi alloying individually. A one-parameter method for fitting the composition dependence of the band gaps of dilute quaternary semiconductor alloys is proposed which is in excellent agreement with data for Ga1−yInyNxAs1−x.

Study of the long-wavelength optic phonons in AlGaInP and AlGaInAs

The investigation of the lattice dynamics of (AlxGa1−x)yIn1−yP quaternary semiconductor alloys lattice matched to GaAs has been made by Raman scattering. The Raman spectra exhibit three-mode behavior depending on the composition. A modified random element isodisplacement (MREI) model is generalized to the III–V (AxB1−x)1−yCyD-type quaternary alloys, describing the behavior of the optical phonons. The calculated result of two quaternary mixed crystals, (AlxGa1−x)yIn1−yP and (AlxGa1−x)yIn1−yAs, is in good agreement to the experimental data.

Optical functions of chalcopyrite CuGa x In 1-x Se 2 alloys

We report pseudodielectric functions of the quaternary semiconductor alloys CuGaxIn1-xSe2. Measurements were done in polycrystalline samples from 0.7 to 5.2 eV at room temperature by spectral ellipsometry. Accurate values of refractive indices n and extinction coefficients k representative of the bulk materials are obtained from the data. The structures observed in are analyzed by fitting the numerically differentiated spectra of d2 (ω)/dω2 to analytic line shapes. The obtained energies are related to given inter-band transitions by taking into account the electronic band structures of the ternary end-point compounds.

Optimization of III–V compound semiconductor heterostructures for distributed Bragg reflector applications in VCSELs

A selectively oxidized vertical cavity surface emitting laser (VCSEL) has been designed and fabricated for operation at a wavelength of 1.546 μm. The device structure was grown on an InP substrate using III–V quaternary semiconductor alloys for the two mirror stacks and unstrained multi-quantum wells for the active layer. A threshold current as low as 2.2 mA has been achieved. The influence of the intentional and growth-related compositional grading at the heterointerfaces on the mirror reflectivity and laser characteristics has been investigated, and key sensitivities to laser performance have been determined.

Design and performance of a vertical cavity surface emitting laser based on III-V quaternary semiconductor alloys for operation at 1.55 μm

A highly efficient Vertical Cavity Surface Emitting Laser (VCSEL) has been designed and fabricated for operation at a wavelength of 1.546 /spl mu/m. The device design incorporates optimized Bragg mirrors with minimized number of periods. The present structure employs quaternary III-V semiconductor alloys with GaInAsP as the active layer and AlGaInAs/InP multilayer stack as the Distributed Bragg Reflector (DBR). The material parameters of the quaternary alloys including index of refraction and bandgap energy are calculated over the entire composition range. The difference in the indices of refraction between AlGaInAs and InP alternating layers is found to be 0.46 resulting in a significant reduction of the number of DBR layers. The MBE technique is employed for the epitaxial VCSEL structure growth and the selective oxidation of AlInAsP single layer is used to form the current confinement aperture. The VCSEL gain performance has been calculated and measured, resulting in the experimental threshold current of about 3 mA and the output power of 1 mW.

Calculations of Dielectric Constant for AlGaInAs Quaternary Semiconductor Alloy in the Transparent Region and Above (0.4-4.0eV)

AbstractThe modeling of the spectral behavior of the refractive index of AlGaInAs quaternary IIIV semiconductor alloy in the energy range from 0.4 to 4eV, including the transparent region, is presented. The extended model of interband transition contributions incorporates not only the fundamental absorption edge contribution to the dielectric function, but also contributions from higher energy and indirect transitions. It is demonstrated that indirect energy transitions must be included in the calculations of the complex dielectric function of the material in the transparent region. Indirect transitions from different critical points in the Brillouin zone are treated separately. The comparison between the theoretical refractive indices and the experimental data for AlGaInAs alloy is presented. These calculations have been applied to the design of Bragg mirrors with the highest refractive index contrast for heterostructure lasers.