High Hole Mobility Polycrystalline GaSb Thin Films

In this paper, we report on the structural and electronic properties of polycrystalline gallium antimonide (poly-GaSb) films (50–250 nm) deposited on p+ Si/SiO2 by metalorganic vapour phase epitaxy at 475 °C. GaSb films grown on semi-insulating GaAs substrates are included as comparative samples. In all cases, the unintentionally doped GaSb is p-type, with a hole concentration in the range of 2 × 1016 to 2 × 1017 cm−3. Exceptional hole mobilities are measured for polycrystalline GaSb on SiO2 in the range of 9–66 cm2/Vs, exceeding the reported values for many other semiconductors grown at low temperatures. A mobility of 9.1 cm2/Vs is recorded for an amorphous GaSb layer in a poly-GaAs/amorphous GaSb heterostructure. Mechanisms limiting the mobility in the GaSb thin films are investigated. It is found that for the GaSb grown directly on GaAs, the mobility is phonon-limited, while the GaSb deposited directly on SiO2 has a Coulomb scattering limited mobility, and the poly-GaAs/amorphous GaSb heterostructure on SiO2 displays a mobility which is consistent with variable-range-hopping. GaSb films grown at low temperatures demonstrate a far greater potential for implementation in p-channel devices than for implementation in ICs.

Chemical Mechanical Polishing of GaSb Wafers for Significantly Improved Surface Quality

Gallium antimonide (GaSb) is considered an ideal substrate for heterostructure growth via molecular beam epitaxy. A significant aspect that inhibits the widespread application of infrared plane-array detector growth on GaSb is the starting substrate surface quality. In this study, the chemical mechanical polishing of GaSb wafers is investigated by considering the effects of the polishing pad, polishing solution, polishing time and pH buffer on their surface morphology and roughness. The surface morphology and root mean square (RMS) roughness of the free-standing wafers are characterized using a white light interferometer, a laser interferometer and an atomic force microscope. X-ray tomography is employed to measure the surface crystalline quality and strain defects of the samples subjected to the polishing treatments. The results show that with the optimum polishing condition, the polished GaSb wafers demonstrate high-quality surfaces without haze, scratches or strain defect regions. The peak to valley value is 5.0 μm and the RMS roughness can be controlled at less than 0.13 nm. A buffer layer grown on the GaSb surface with molecular beam epitaxy is examined via atomic force microscopy and high-resolution X-ray diffraction, which show a low RMS roughness of 0.159 nm, a well-controlled two-dimensional growth mode and a full width half maximum of the Bragg diffraction peak of 14.2”, indicating high-quality GaSb wafers. Thus, this work provides useful guidelines for achieving GaSb wafers with high-quality surfaces that show significant promise for substrate applications.

Cytotoxicity and pro-inflammatory effect of GaSb thin films in L929 cells

Gallium antimonide (GaSb)-based devices operate efficiently in the infrared region. Investigating the toxicity of GaSb thin film is necessary for using embedded GaSb-based devices in living organisms. In this study, viability, oxidative stress, inflammatory responses, apoptosis induction and genotoxicity of GaSb were assayed using L929 cells following a 24 h exposure to GaSb. GaSb thin films were deposited on a quartz substrate using radio frequency (RF) magnetron sputtering. These films were soaked in cell culture medium to prepare test solutions. The viability of cells treated with the GaSb extract was lower than that of control cells. GaSb elicited little reactive oxygen species (ROS) generation. Tumor necrosis factor (TNF)-[Formula: see text] and interleukin (IL)-1[Formula: see text] levels were elevated in GaSb-treated cell culture supernatants. Apoptosis and genotoxicity were not evident following GaSb treatment. Overall, these results demonstrate the low toxicity of GaSb compared with previous studies examining arsenic-containing III–V materials, which is desirable for biological devices.

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.

Ohmic contacts to n-type and p-type gallium antimonide whiskers

The ohmic contacts to the n-type conductivity gallium antimonide whiskers were created due to a current pulse shaper. It was established that I–V characteristics of GaSb whiskers at low temperatures are linear, regardless of the direction of current transmission. That allows using the investigated techniques to create electrical contacts and study their electrophysical characteristics. GaSb samples with a diameter of 12 μm and 20 μm were studied at temperatures 4.2 K and 77 K. A slide table with bath and microfurnace was made for welding ohmic contacts to GaSb whiskers. Gold microwire with a diameter of 30 μm was used as a contact material. The melting was carried out under the flux layer. It was revealed that the fusion is one of the most suitable methods for creating contacts to the whiskers grown by gas transport reactions.

Manganese segregation on defects of a crystall lattice GaSb

When doping gallium antimonide with 2 at.% Mn, it was found that, as a result of quenching of the melt, manganese segregates on grain-forming dislocations of the crystalline GaSb (111) texture in the form of microinclusions based on the ferromagnetic compound MnSb. Manganese atoms segregate on GaSb dislocations discretely with periodic spacing of inclusions from each other. The dimensions of the inclusions are of the order of 1 μm, they differ in composition and magnetic properties, but on average their composition and properties correspond to the ferromagnetic phase Mn1,1Sb. At T = 4 K, the crystalline anisotropy of GaSb <Mn> is accompanied by magnetic anisotropy; at T = 300 K, spherical clusters of a magnetic semiconductor retain the properties of a soft magnetic ferromagnet with a coercive force Hc ≈ 10 E.