GaSb Materials Research Articles

Research on wet etching techniques for very long-wavelength InAs/GaSb superlattices

Manufacturing high-quality very long-wavelength infrared detectors (VLWIR) on GaSb substrate is significant for advancing the superlattices application in the field of infrared detection. In this study, superlattices with excellent surface and crystal quality were obtained. Based on it, we delved into the wet chemical etching fabrication for very long-wavelength InAs/GaSb superlattices. The impact of varying concentrations of different components on surface etching results along the growth direction was examined through univariate experiments. The analysis revealed that the concentration and ratios of phosphoric acid and hydrogen peroxide notably dictated both the etching rate and surface roughness. The surface chemistry of GaSb and InAs bulk materials treated with various etching solution components was investigated using X-ray photoelectron spectroscopy (XPS). The objective of this study is to provide a comprehensive understanding of the effects caused by different components in wet etching, thereby enhancing the understanding of the wet etching process for InAs/GaSb materials.

Microscale Engineering of n-Type Doping in Nanostructured Gallium Antimonide: AC Impedance Spectroscopy Insights on Grain Boundary Characterization and Strategies for Controlled Dopant Distribution.

This paper investigates the microscale engineering aspects of n-type doped GaSb to address the challenges associated with achieving high electrical conductivity and precise dopant distribution in this semiconductor material. AC impedance spectroscopy is employed as a reliable technique to characterize the microstructural and electrical properties of GaSb, providing valuable insights into the impact of grain boundaries on overall electrical performance. The uneven distribution of dopants, caused by diffusion, and the incomplete activation of introduced dopants pose significant obstacles in achieving consistent material properties. To overcome these challenges, a careful selection of alloying elements, such as bismuth, is explored to suppress the formation of native acceptor defects and modulate band structures, thereby influencing the doping and compensator formation processes. Additionally, the paper examines the effect of microwave annealing as a potential solution for enhancing dopant activation, minimizing diffusion, and reducing precipitate formation. Microwave annealing shows promise due to its rapid heating and shorter processing times, making it a viable alternative to traditional annealing methods. The study underscores the need for a stable grain boundary passivation strategy to achieve significant improvements in GaSb material performance. Simple grain size reduction strategies alone do not result in better thermoelectric performance, for example, and increasing the grain boundary area per unit volume exacerbates the issue of free carrier compensation. These findings highlight the complexity of achieving optimal doping in GaSb materials and the importance of innovative analytical techniques and controlled doping processes. The comprehensive exploration of n-type doped GaSb presented in this research provides valuable insights for future advancements in the synthesis and optimization of high-conductivity nanostructured n-type GaSb, with potential applications in thermoelectric devices and other electronic systems.

GaSb Film is a Saturable Absorber for Dissipative Soliton Generation in a Fiber Laser

Nanotechnology is at the forefront of scientific research and offers great prospects for the development of technology. As a type of III-V semiconductor, GaSb materials exhibit numerous outstanding optical and electrical characteristics that are very promising for nonlinear optical device applications. In this study, the electronic band structures of GaSb are theoretically calculated, and its application in dissipative soliton fiber lasers is validated. A GaSb thin film is deposited on a microfiber using magnetron sputtering deposition, and the morphology, chemical composition, structure, and nonlinear optical characteristics of the proposed microfiber-GaSb device are investigated. After incorporating it into an Er-doped fiber laser, dissipative soliton laser pulses are readily obtained with a fundamental frequency of 43.5 MHz. With increasing pump power, the fiber laser could work in the fundamental frequency mode-locking state. At a pump power of 570 mW, the pulse width and the output power are measured to be 917 fs and 49.75 mW, separately. These results reveal that GaSb can be used as an efficient saturable absorber, which will have potential applications in ultrafast optics.

Pinhole-seeded lateral epitaxy and exfoliation of GaSb films on graphene-terminated surfaces

Remote epitaxy is a promising approach for synthesizing exfoliatable crystalline membranes and enabling epitaxy of materials with large lattice mismatch. However, the atomic scale mechanisms for remote epitaxy remain unclear. Here we experimentally demonstrate that GaSb films grow on graphene-terminated GaSb (001) via a seeded lateral epitaxy mechanism, in which pinhole defects in the graphene serve as selective nucleation sites, followed by lateral epitaxy and coalescence into a continuous film. Remote interactions are not necessary in order to explain the growth. Importantly, the small size of the pinholes permits exfoliation of continuous, free-standing GaSb membranes. Due to the chemical similarity between GaSb and other III-V materials, we anticipate this mechanism to apply more generally to other materials. By combining molecular beam epitaxy with in-situ electron diffraction and photoemission, plus ex-situ atomic force microscopy and Raman spectroscopy, we track the graphene defect generation and GaSb growth evolution a few monolayers at a time. Our results show that the controlled introduction of nanoscale openings in graphene provides an alternative route towards tuning the growth and properties of 3D epitaxial films and membranes on 2D material masks.

A Review on Thermophotovoltaic Cell and Its Applications in Energy Conversion: Issues and Recommendations.

Generally, waste heat is redundantly released into the surrounding by anthropogenic activities without strategized planning. Consequently, urban heat islands and global warming chronically increases over time. Thermophotovoltaic (TPV) systems can be potentially deployed to harvest waste heat and recuperate energy to tackle this global issue with supplementary generation of electrical energy. This paper presents a critical review on two dominant types of semiconductor materials, namely gallium antimonide (GaSb) and indium gallium arsenide (InGaAs), as the potential candidates for TPV cells. The advantages and drawbacks of non-epitaxy and epitaxy growth methods are well-discussed based on different semiconductor materials. In addition, this paper critically examines and summarizes the electrical cell performance of TPV cells made of GaSb, InGaAs and other narrow bandgap semiconductor materials. The cell conversion efficiency improvement in terms of structural design and architectural optimization are also comprehensively analyzed and discussed. Lastly, the practical applications, current issues and challenges of TPV cells are critically reviewed and concluded with recommendations for future research. The highlighted insights of this review will contribute to the increase in effort towards development of future TPV systems with improved cell conversion efficiency.

Carrier heating and its effects on the current-voltage relations of conventional and hot-carrier solar cells: A physical model incorporating energy transfer between carriers, photons, and phonons

Theoretical models and frameworks are developed to investigate the effects of carrier heating on conventional and hot-carrier solar cells. They incorporate intraband carrier energy relaxation into the Shockley-Queisser model for conventional solar cells and the Ross-Nozik model for hot-carrier solar cells. Explicit formulas are presented to calculate intraband carrier energy relaxation rates via the interactions of polar longitudinal optical phonons and deformation-potential longitudinal and transverse optical phonons. These formulas incorporate the decay processes and phonon bath sharing of optical phonons. The effects of carrier heating on the current-voltage characteristics of conventional and hot-carrier solar cells are investigated and discussed for GaAs, InP, GaSb, and InAs materials. This paper will particularly discuss the differences between extraction cooling in hot-carrier solar cells and recombination heating from stimulated photon emissions in semiconductor lasers. It will prove that carriers in hot-carrier solar cells need to be extracted with a selective-contact energy larger than their quasi-Fermi-level separation in order to make devices work with extraction cooling, rather than recombination heating.

Study of wet and dry etching processes for antimonide-based photonic ICs

We report on the dry etch process parameters and the associated etch rates for target and mask materials, as well as surface roughness in an inductively coupled plasma (ICP) for the (AlGaIn)(AsSb)-compounds. The essential chemistry is based on Cl2 with the addition of N2 for sidewall passivation. The optimized ICP etch process is capable of producing high aspect ratio structures with smooth sidewalls. In situ reflectance monitoring with a 670-nm-wavelength laser was used to enable stop-etching at a material interface with high accuracy. Given the additional need for highly selective wet chemical etchants in the fabrication of GaSb based electronic and optoelectronic devices, an extensive investigation was also performed to examine numerous etch solutions. These etchants were listed with etch rates, selectivities, and surface roughness in order to validate their suitability for intended applications. Despite the frequent use of GaSb or InAsSb materials for etch stop layers against each other, devices where their unique type-II broken bandgap alignment is undesired require new selective wet etchants between GaSb and AlGaAsSb with good selectivity. All of the wet chemical and dry etching processes described here were optimized using an n-type GaSb substrate.

Development of a Long-Wave Infrared Band-Edge (LWIR BE) thermometry instrument.

Accurate measurement of substrate temperature is one of the most critical process control parameters for molecular beam epitaxy (MBE) growth. Band-edge thermometry instruments have proven to be a valuable tool for process control during MBE growth of semiconductor films, providing as high as ±1 °C temperature resolution. The increasing use of InAs, GaSb, and AlSb iii-v materials necessitates a method for accurately measuring the temperature of their closely lattice-matched GaSb substrates. Current-technology instruments typically rely on InGaAs detector materials which have a maximum wavelength λ detection of ∼1.7 μm, but GaSb substrates have a band gap energy corresponding to λ > 2 μm. A band-edge thermometry instrument capable of λ > 2 μm has been developed using an InAs/InGaSb strained-layer superlattice detector sensitive to 2-9.5 μm long-wave IR wavelengths.

2~5 μm中红外波段GaSb半导体材料研究进展

III-V族半导体材料因其光电子应用中的优势而备受关注。这些材料中，GaSb和GaSb相关半导体材料因具有高的载流子迁移率和较窄的禁带宽度而被认为是中红外波段光电子半导体器件的首选材料。然而，半导体光电子器件的性能强烈依赖于材料的结构和光学性质，所以GaSb材料的研究工作重点是如何提高晶体质量，精确调整合金组分，提高发光性能等。本文对2~5 μm GaSb和GaSb相关半导体材料的外延生长和材料性质的研究进展做出了简要的概述，主要讨论了GaSb材料、GaSb合金薄膜材料以及GaSb基量子阱材料的外延生长过程及材料性质，以期获得GaSb基半导体材料外延生长的最优条件。 III-V group semiconductors have received a great deal of attention because of their potential ad-vantages for use in optoelectronic and electronic applications. Among these materials, with characteristics that include high carrier mobility and a narrow band gap, gallium antimonide (GaSb) and GaSb-related semiconductors have been recognized as most suitable candidates for high-per- formance optoelectronics in the mid-infrared range. The performance of semiconductor devices, however, strongly dependent on the structure and optical properties of materials, so the GaSb materials research focus is to improve the quality of crystal, adjust the alloy composition, improve the luminous performance, etc. In this paper, the progress of epitaxial growth and material properties of 2 - 5 μm GaSb and GaSb-related semiconductor materials are briefly reviewed. The epitaxial growth processes and material properties of GaSb, GaSb related alloy materials and GaSb- based quantum well materials are discussed in order to obtain the optimal conditions for epitaxial growth of GaSb-based semiconductor materials.

等离子体氮钝化GaSb材料表面特性研究

等离子体氮钝化GaSb材料表面特性研究

Brief Review of Epitaxy and Emission Properties of GaSb and Related Semiconductors

Groups III–V semiconductors have received a great deal of attention because of their potential advantages for use in optoelectronic and electronic applications. Gallium antimonide (GaSb) and GaSb-related semiconductors, which exhibit high carrier mobility and a narrow band gap (0.725 eV at 300 K), have been recognized as suitable candidates for high-performance optoelectronics in the mid-infrared range. However, the performances of the resulting devices are strongly dependent on the structural and emission properties of the materials. Enhancement of the crystal quality, adjustment of the alloy components, and improvement of the emission properties have therefore become the focus of research efforts toward GaSb semiconductors. Molecular beam epitaxy (MBE) is suitable for the large-scale production of GaSb, especially for high crystal quality and beneficial optical properties. We review the recent progress in the epitaxy of GaSb materials, including films and nanostructures composed of GaSb-related alloys and compounds. The emission properties of these materials and their relationships to the alloy components and material structures are also discussed. Specific examples are included to provide insight on the common general physical and optical properties and parameters involved in the synergistic epitaxy processes. In addition, the further directions for the epitaxy of GaSb materials are forecasted.

Análisis de desempeño de conmutadores de microondas tipo serie-paralelo y TEE de diferentes materiales semiconductores para comunicaciones Satelitales

Se presenta un análisis de desempeño de conmutadores de microondas compuestos, de una entrada y una salida (SPST), diseñados con diodos p-i-n tipo masa con diferentes tipos de materiales semiconductores para las bandas de frecuencia Ku y Ka. Las dos configuraciones de conmutadores compuestos más comunes son aquellos con diodos p-i-n ubicados en diseños serie-paralelo y serie-paralelo-serie (TEE) y aquí son analizados utilizando materiales semiconductores de Si, GaAs, GaN-WZ, GaN-ZB, GaSb, InP y SiC. Se presenta la metodología utilizada en los cálculos de resistencia serie y capacitancia de unión en los diodos p-i-n con el propósito de calcular los parámetros de desempeño propios de cada dispositivo conmutador. Estos parámetros son pérdida de inserción y aislamiento. Los conmutadores de tipo serie-paralelo, exceptuando el conmutador basado en diodo p-i-n de SiC-6 H, exhiben pérdidas de inserción menores a 0.2 dB y aislamiento hasta 41dB a la frecuencia de operación de 12 GHz. El conmutador diodo p-i-n tipo TEE con base en GaN-ZB tiene la mejor respuesta de pérdida de inserción menor a 0.23 dB y aislamiento hasta 52 dB, a las frecuencias de operación de 12 GHz y 30 GHz. El conmutador compuesto con base en diodo p-i-n de GaSb alcanza el mejor desempeño a la frecuencia de 12 GHz. Los conmutadores de microondas con configuración TEE tienen respuestas satisfactorias para la frecuencia de 30 GHz.

Origin of the reverse optical-contrast change of Ga-Sb phase-change materials—Anab initiomolecular-dynamics study

A large number of phase-change materials (PCMs) have been developed experimentally; however, only Ge2Sb2Te5-based PCMs have been significantly explored using ab initio molecular-dynamics (AIMD) simulations. We present an AIMD study of the full melt/quench/anneal PC cycle for Ga-Sb materials, namely, the stoichiometric composition, GaSb, and the near-eutectic alloy, Ga16Sb84. The calculated electronic densities of states and optical reflectivities are compared between the amorphous and crystalline phases for both compositions, and it is shown that the contrasting opto-electronic properties of each crystalline material can be attributed to different structural transformations of Ga and Sb on crystallization from the amorphous state.

Features of defect formation during the growth of double heterostructures for injection lasers based on Al x Ga1 − x As y Sb1 − y /GaSb materials

A lack of lattice defects and, in particular, a lack of dislocations in the active layer in complex multilayer heteroepitaxial systems is the basic condition for the efficient and reliable operation of optoelectronic microdevices. Minimum elastic stresses in multilayer heteroepitaxial systems and their lack in the active layer at that elevated temperature that occurs in an efficiently operating electronic device is the second necessary condition for its long-term operation.

Localized surface plasmon resonances in highly doped semiconductors nanostructures

We demonstrate the occurrence of localized surface plasmon resonances (LSPRs) in periodic arrays of highly doped/un-doped InAsSb/GaSb semiconductor nanostructures, where highly doped InAsSb is degenerated and exhibits a metallic behavior while being lattice-matched onto GaSb. Reflectance spectroscopy allows investigating the impact of the geometrical and physical properties of both InAsSb and GaSb materials on the LSPR. Our results show that these InAsSb/GaSb nanostructures form the building blocks of metal-free, all-semiconductor infrared plasmonic devices.

Growth of type II strained layer superlattice, bulk InAs and GaSb materials for minority lifetime characterization

We have examined the growth of strained layer superlattice (SLS) structures for the purpose of characterizing and improving the minority carrier lifetime. Structures with different SL periods but with same absorption wavelength were first studied. Despite a doubling of the number of interfaces per thickness unit, no significant change was seen in the carrier lifetime. This observation points away from the interfaces as the location of lifetime limiting defect centers. To gain further insights into the spatial location of the defect centers, a series of binary InAs and GaSb layers grown with different substrate temperatures, were studied. We found that higher growth temperatures were beneficial for both binaries, although the improvement for GaSb was less than that of InAs. The substrate temperature was also varied in SLS structures and characterized with high-resolution x-ray diffraction. By using the peak width from the SLS zero-order diffraction as a figure of merit, we found a shallow growth window of ∼±20° around an optimum temperature of 440°C. Outside this temperature window the material quality deteriorated very rapidly. Unfortunately, the substrate temperatures that would provide an improvement in the binary lifetimes fall mainly above the SLS growth window, thus limiting this parameter as a means of improving lifetimes in the SLS. A model that qualitatively relates bulk and SLS lifetimes through native defects is proposed and strategies for improving the lifetimes are discussed.

Effects of Surface Orientation on the Performance of Idealized III–V Thin-Body Ballistic n-MOSFETs

Ballistic on-currents of thin-body n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) are compared across group IV (Si, Ge) and III-V (InAs, In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> As, GaAs, GaSb) materials for different body thickness values, surface orientations, and transport directions under several idealization assumptions. Previous simulation studies have shown that, as oxide capacitance increases, typical III-V channels with (100) surface perform worse than Si in the ballistic limit due to the degraded density-of-states (DOS). In this letter, simulation results based on tight-binding band structure calculations verify a recent proposal that confined III-V n-MOSFETs with small Γ-L separations overcome the DOS bottleneck and deliver high injection velocities, boosting on-current performance. By using the quantized L-valleys, GaSb with (100) or (111) surface orientations shows the best ballistic performance, outperforming all other materials. Although GaAs (100) and InAs or In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> As with any surface orientation suffer from the DOS bottleneck, GaAs (111) gives higher ballistic on -currents than Si does.

The crystallization behavior of stoichiometric and off-stoichiometric Ga–Sb–Te materials for phase-change memory

The stoichiometric Ga4Sb6Te3 and Ga–Sb materials were systemically studied. The alloy Ga4Sb6Te3 shows a fast crystallization speed, very high crystallization temperature, Tx, and high electrical contrast. Although stoichiometric GaSb has similar performance and even faster crystallization speed, the electrical contrast is much lower. The other off-stoichiometric compounds we studied all have higher Tx than Ge2Sb2Te5 indicating a good amorphous stability. By raising the Sb/Te ratio with GaSb incorporation, Tx and the recrystallization time of melt-quenched, amorphous samples can be effectively increased. The stoichiometric Ga4Sb6Te3 with less likelihood of phase-segregation compared to nonstoichiometric compounds is a promising candidate for phase-change memory.

Raman spectroscopic determination of hole concentration in p-type GaSb

Phonon-plasmon coupled mode Raman spectra of p-type GaSb were measured at room temperature as a function of hole concentration. These spectra were obtained using an optical system based on 752.55nm excitation in order to obtain more sensitivity to bulk GaSb coupled mode Raman scattering than is possible with visible wavelength excitation-based systems. A relatively simple spectral model for the electronic contribution to the dielectric function was evaluated for determination of hole concentration from the bulk coupled mode spectra. The hole concentration was determined from the Raman spectra by minimizing the sum of the squared residuals between a measured and simulated spectrum as a function of total hole concentration and a plasmon damping parameter. The hole concentrations determined from the fit to the Raman spectra were compared to the hole concentrations determined from single magnetic field Hall effect measurements that were corrected to account for two band conduction. The hole concentrations determined using the two methods differed by ≈3% to ≈33% for single magnetic field Hall effect hole concentrations from ≈5.51×1017to≈6.38×1018cm−3. The agreement between the hole concentrations determined using the two methods was worse for single magnetic field Hall effect hole concentrations below ≈5.51×1017cm−3. In general, compared to the hole concentrations determined from Hall effect measurements corrected to account for two band conduction, the hole concentrations determined from the Raman spectra were higher for epilayers with the lower Hall effect hole concentrations and lower for the epilayer with the highest Hall effect hole concentration. The deviations between the two methods were attributed to the limitations of the spectral model employed and uncertainties in GaSb materials properties.

Raman Spectroscopy of n-Type and p-Type GaSb with Multiple Excitation Wavelengths

The interpretation of Raman spectra of GaSb can be complicated by the presence of a so-called surface space-charge region (SSCR), resulting in an inhomogeneous near-surface Raman scattering environment. To fully interpret Raman spectra, it is important to have an understanding of the SSCR profile relative to the Raman probe depth. However, a priori determination of even the actual SSCR width is not always possible for GaSb under a wide range of doping levels. The primary objective of this report is to provide a convenient reference to aid in the determination of relative contributions to an observed GaSb Raman spectrum of SSCR scattering and bulk scattering for a range of excitation wavelengths, doping levels, and SSCR widths and types. Raman spectra of both n-type and p-type doped GaSb epilayers were obtained using 488 nm, 514.5 nm, 647.1 nm, and 752.55 nm excitation radiation. Both n-type and p-type doped GaSb epilayers were selected for investigation because these layers exhibit the two different SSCR types that are typically encountered with as-grown GaSb and related materials. A range of doping levels were examined for each doping type so as to examine the effects of a varying SSCR width on the observed spectra. A secondary objective of this report is to demonstrate the performance of a spectroscopic system based on 752.55 nm excitation that is sensitive to bulk carrier properties in n-type and p-type doped GaSb epilayers over a wide doping range, unlike visible-wavelength-based optical systems.