GaSb Crystals Research Articles

Effect of N2-H2 remote plasma nitridation temperature on surface properties of Te-doped GaSb crystals

GaSb is regarded as one of the most promising near-infrared optoelectronic materials in recent years. However, due to the ease of natural oxidation of GaSb, the surface will promptly form a thick oxide layer which is highly resistant to removal, resulting in detrimental interface defects and higher surface state density. Although studies have demonstrated the feasibility of plasma for removing oxide, the ultra-high vacuum is necessary for complete removal, which poses challenges for commercial applications. Herein, we optimized the nitrogen plasma passivation process for Te-doped GaSb, combining remote plasma source with Atomic Layer Deposition (ALD) in-situ annealing to modify GaSb (001) surface, which approaches non-damaging treatment. The temperature during passivation will affect nitrogenation on GaSb surface, result in enrichment of metallic Sb when reaching 573 K, and impact emission efficiency. By setting the passivation temperature at 523 K and combining with in-situ annealing, the photoluminescence (PL) efficiency of GaSb has doubled. This demonstrates the validity of low-temperature nitrogen passivation in improving surface state and reducing defect density on GaSb.

Improving the crystal quality and optoelectronic property of GaSb with Al doping

GaSb and Ga1-xAlxSb crystals were prepared with the vertical Bridgman (VB) method. The effects of aluminum atoms (Al) doping on the structure and photoelectric properties of GaSb crystal were investigated. The results show that the GaAlSb crystal maintains the zinc blende crystal structure of the GaSb crystal, and the crystal quality gradually improves with the increase of Al doping concentration, and the effective segregation coefficient keff of Al decreases from 3.69 to 2.83. Furthermore, Al doping significantly inhibits the formation of dislocations, of which density decreases from 3.634 × 103 cm−2 to 1.256 × 103 cm−2. As an element with the same equivalent electrons as Ga, Al doping makes GaSb crystal become into an n-type semiconductor with the free electrons as the main carriers, from a p-type semiconductor with the holes as the main carriers (8.867 × 1017 cm−3). And the carrier concentration, i.e., the free electrons concentration, increases with the doped Al concentration increase, up to the maximum of 1.929 × 1018 cm−3. And the mobility of electron carriers increases with the increase of Al concentration, up to 2.140 × 103 cm2/(V•s), far greater than that of the hole carriers 1.358 × 103 cm2/(V•s). And the resistivity decreases from 7.649 × 10−3 Ω•cm to 1.416 × 10−3 Ω•cm. Moreover, the infrared transmittance spectrum also shows a significant improvement of the crystal quality.

Temperature dynamic compensation vertical Bridgman method growth of high-quality GaSb single crystals

Gallium antimonide (GaSb) is considered an ideal substrate for heterostructure growth. A significant property that inhibits the widespread application of infrared plane-array detector growth on GaSb is the crystal quality of the starting substrate. Herein, we report the growth of single-crystal GaSb by a temperature dynamic compensation vertical Bridgman (TDC-VB) method. This approach offers a low temperature gradient and a stable solid–liquid interface position in the furnace during the growth process. Two inch diameter twin-free GaSb single crystals with (100) orientation have been reproducibly obtained using the TDC-VB method. The crystalline character of the obtained GaSb has been examined by optical microscopy (OM), high-resolution X-ray diffraction (HRXRD), X-ray tomography (XRT), and Fourier-transform infrared (FTIR) spectroscopy. The etch pit dislocation density (EPD) of the GaSb polished wafers (100) was 6–72 cm−2, and the full-width at half-maximum (FWHM) of the Bragg diffraction peak was 15.4″. A uniform XRT image was obtained, and ca. 50 % of the GaSb wafers, which were produced by one crystal, showed transmittance > 20 % at 10 µm, indicating the formation of high-quality GaSb crystals. This work provides useful guidelines for the formation of high-quality GaSb crystals with significant promise for substrate applications.

Effect of double-constrained potential on the ground-state binding energy of magnetopolaron in a quantum well

This study aims at investigating the properties of magnetopolarons (MPs) in III–V compound semiconductors: GaP, GaAs and GaSb crystals. The obtained results from numerical calculation revealed that absolute value of ground-state (GS) binding energy [Formula: see text] of the magnetopolaron is affected by magnetic field, type of crystal as well as the parabolic and asymmetric Gaussian potentials, which leads to a series of interesting phenomena. The study of results obtained provides a good theoretical guidance on optoelectronic devices and quantum information. We have theoretically investigated the origins of these strange phenomena, and our findings provide sound theoretical direction for photoelectric technology and quantum information.

Calculations of Energy Band Structure of GaAs, GaSb and GaP Crystals as a Function of Temperature Using the Semiempirical Tight Binding Method

In this paper, the band structure of gallium group of III-V semiconductor has been calculated with temperature, the semi-empirical tight binding method was used to calculate the band structure and the matrix elements were calculated for both models sp^3 and sp^3 s^*. A computer program in MATLAB was designed to calculate the energy eigenvalues for the wave vector points in the first Brillouin zone between high symmetry points to form energy bands. The effect of temperature on the energy band of these group of crystals has been studied by changing the values of the lattice constant under the influence of temperature according to the Pierron relation and thus calculating the change in the length of the bond with temperature, which in turn affects the change in the values of the elements of the Hamiltonian matrix. The energy gap and refractive index were calculated at points of high symmetry as a function of temperature. The results showed a decrease in the energy gap values of GaAs, GaSb and GaP crystals with increasing temperature. Then the experimental Varshni relation was used to calculate the change in the energy gap values of these crystals and the results obtained from current study were compared with the results of Panish and Bellani, where the results showed that a model sp^3 s^* gives better results than the model sp^3.As well as the calculations of the refractive index of these crystals using the Moss formula showed that the refractive index will gradually increase with increasing temperatures.

Fermi level pinning and hydrostatic pressure effect in electron irradiated GaSb

The effect of 2 MeV electron bombardment up to total electron dose of on the electrical and piezo resistive properties of n- and p-type GaSb crystals was studied. The electron irradiation leads to saturation of the hole concentration at about as a result of Fermi level pinning near the valence band top in all irradiated samples. With this in mind, the calculated data on the energy position of the charge neutrality level in GaSb were analyzed. The pressure coefficient of resistivity was measured as a function of Fermi level position in the electron irradiated samples. Isochronal annealing of radiation-induced defects was investigated in the temperature range of 20–400 °C.

Effect of temperature gradient on microstructure and properties of GaSb crystals grown with Bridgman method

GaSb crystal ingots were grown with vertical Bridgman method. The effects of temperature gradient on the structure and properties of GaSb crystals were investigated. When the temperature gradient increased from 5 to 7 °C cm−1, the crystallinity of the ingot improved, the dislocation density decreased by 55%, from 3928 to 1785 cm−2; the carrier mobility increased by 29.6%, from 868 to 1125 cm2 V−1 · s−1; the resistivity decreased 50.6%, from 12.45 to 6.332 × 10–3 Ω · cm; the infrared transmission increased from 27% to 32%. When the temperature gradient increased from to 7 to 9 °C cm−1, the crystallinity of the ingot deteriorated obviously, the dislocation density increased 4.38 times, from 3928 to 9609 cm−2; the carrier mobility decreased by 52.4%, from 1125 to 738 cm2 V−1 · s−1; the resistivity increased 6.2 times, from 6.332 to 23.94 × 10–3 Ω · cm; the infrared transmission decreased from 32% to 25%.

Real-time in situ observation of extended defect evolution near a crack tip in GaSb crystal under thermal loading

When an AlAsSb/InAs superlattice semiconductor material is grown by molecular beam epitaxy, extended defects in the GaSb buffer layer are inevitable. Therefore, the study the formation and evolution of extended defects is considerably important. In this study, a crack tip located in the buffer layer was considered. The evolution process of nucleation as well as development and extinction of two extended defects on the (1 1 −1) and (−1 1 −1) faces were observed in real time in situ by scanning transmission electron microscopy during heating. Analysis of the stress field results showed that thermal stress is the driving force for the propagation of extended defects, which promotes the nucleation and evolution of the (1 1 −1) and (−1 1 −1) surface extended defects. The variation in crack width before and after heating was measured according to the intensity of the atomic and crack regions in the high-resolution STEM-BF image. The results showed that the crack closes after heating at a high temperature compared to room temperature. It is considered that the amorphous GaSb at the crack tip and the edge portion at the nanometer scale during the heating process is transformed into a single crystal, thus causing the crack to shrink.

Growth of GaSb Crystal and Evaluation of Its Thermoelectric Properties Along (111) Plane

AbstractIn this study, group III–V compound semiconductor gallium antimonide (GaSb) crystal is grown by the vertical Bridgman technique. A (111) twinning is generated in the as‐grown crystal due to its polarity behavior as the GaSb crystal has a zinc‐blende structure. Hall effect measurements illustrate that the as‐grown GaSb crystal has n‐type semiconductor behavior among the whole temperature range, and the carrier concentration reaches the highest value of 3.27 × 1018 cm3 at 900 K. Thermoelectric behavior of GaSb crystals along the (111) plane is investigated. It shows the lowest electrical conductivity of 53.2 S cm−1 and the highest Seebeck coefficient of −470.0 µV K−1 at 700 K. However, the largest power factor of 13.7 µW cm K−2 takes place at 600 K. For thermal conductivity (k), the k value always decreases with increasing temperature, and the lowest k that occurred at around 900 K is about 7.44 W m−1 K−1. Finally, a maximum figure of merit of 0.082 is obtained at 700 K.

Enhanced thermoelectric properties of InSb: Studies on In/Ga doped GaSb/InSb crystals

In/Ga elements were doped in GaSb/InSb crystals respectively, and their thermoelectric performances were studied. The crystals had cubic zinc blende structure with change in lattice parameters. The charge transfer occurred between all the three (In, Ga and Sb) elements when In was doped with GaSb. Whereas in Ga doped InSb crystals, the charge transfer occurred only among Ga and Sb elements. In/Ga doped GaSb/InSb crystals exhibited degenerate and non-degenerate electrical properties, respectively. Optical modes of phonon vibrations were present, and their transverse mode was dominant over longitudinal mode in all the samples. The thermoelectric figure of merit (ZT) of In doped GaSb crystals were low because of their low power factor and high thermal conductivity. The highest power factor (59.5 μW/cmK2) and ZT (0.56) at 573 K were achieved by Ga doped (1 × 1021/cm3) InSb crystal. The ZT 0.56 at 573 K is thus far the highest among other reported values of InSb crystals.

Effects of ampoule coating technology on carbon film and GaSb crystals

A carbon film was deposited on the inner wall of a quartz crucible by vacuum evaporation. The effects of gas pressure in the crucible on the carbon film surface morphology and the binding force between the carbon film and the inner wall of the quartz crucible were studied. When the gas pressure was increased from 4 Pa to 12 Pa, the surface roughness of the carbon film increased and large particles appeared on the surface, whereas the binding force between the carbon film and the inner wall of the crucible weakened. When the gas pressure was 12 Pa, the carbon film peeled off. GaSb crystal ingots were prepared by the vertical Bridgman method, and the effects of the carbon film on the ingots’ microstructure and properties were studied. When there was no carbon film on the inner wall of the crucible, the dislocation density of the crystals was the highest, their hardness and resistivity values were the largest, and their carrier mobility was the lowest. When the gas pressure was 4 Pa, the crystal surface was flat and the dislocation density of the crystals significantly decreased. The hardness and resistivity values also decreased and the carrier mobility significantly increased. When the gas pressure was 12 Pa, the hardness and resistivity values of the crystals gradually increased, whereas the carrier mobility gradually decreased.

Chemical-dynamic polishing of InAs, InSb, GaAs and GaSb crystals with (NH<sub>4</sub>)<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>-HBr-citric acid etching composition

Chemical-dynamic polishing of InAs, InSb, GaAs and GaSb crystals with (NH<sub>4</sub>)<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>-HBr-citric acid etching composition

Effects of thermal annealing on structural and electrical properties of surface-activated n-GaSb/n-GaInP direct wafer bonds

A study on the microstructure of argon-beam activated n-GaSb/n-Ga0.32In0.68P bond interfaces is presented, focusing on the behavior of the bond upon thermal annealing and the relationship with electrical bond properties. Structural investigations of annealed samples utilizing high-resolution transmission electron microscopy combined with energy dispersive x-ray spectroscopy are discussed and compared with electrical current-voltage measurements. An amorphous interlayer of ∼1.4 nm thickness between the n-GaSb and n-Ga0.32In0.68P originates from the argon sputtering process. This layer continuously recrystallizes upon thermal annealing, creating a mostly crystalline interface at an annealing temperature of 500 °C. Additionally at 400 °C, In enrichment is observed in the near-surface regions of GaSb and pores are generated at the interface. At 500 °C, larger pores are observed and the In enrichment continues, leading to the formation of crystalline In precipitates within the GaSb crystal. The observed changes in the interfacial microstructure upon annealing correlate with variations in the electrical bond resistances. All bonds show ohmic IV-characteristics with resistances in the range of few mΩcm2. However, the bond resistance decreases after annealing at temperatures up to 350 °C but increases after annealing at higher temperatures. This behaviour agrees with the observation of reduced amorphous layer thickness upon annealing and with the formation of new induced interfacial defects for annealing temperatures above 350 °C.

Chemical interaction of InAs, InSb, GaAs, and GaSb crystal surfaces with (NH4)2Cr2O7–HBr–citric acid etching solutions

We have studied the chemical dissolution of InAs, InSb, GaAs, and GaSb crystals in (NH4)2Cr2O7–HBr–C6H8O7 solutions. The dissolution rate of the crystals has been measured as a function of etchant composition, and the kinetics of the chemical interaction of the semiconductors with solutions have been investigated in detail. The dissolution rate has been shown to be diffusion-limited. Citric acid helps to reduce the etch rate and improves the polishing performance of the etching solutions.

High‐Quality GaSb and GaInSb Crystals Prepared by Vertical Bridgman Method

AbstractHigh‐quality GaSb and Ga1‐xInxSb (x = 0.14) crystals were grown via the vertical Bridgman (VB) method. The lattice structure, morphology, optical, and transport properties of the GaSb and GaInSb crystals were characterized. The influence of the indium doping on the physical properties of the GaSb crystal was also investigated. The results demonstrate that the indium doping maintains the zinc‐blende lattice structure of the GaSb crystal. The segregation of indium is very low, with the radial and axial concentration variation of 2.32% and 4.84%, respectively. The indium doping significantly reduces the dislocation density down to 1.275 × 103 cm−2. The band gap of the indium‐doped GaSb is reduced to 0.549 eV, consistent with the decreased infrared transmission measured by FTIR. Surprisingly, the indium doping changes the majority carrier type of the crystal, from p‐type in the pristine GaSb crystal to n‐type in the GaInSb crystal. Compared to the GaSb crystal, the GaInSb crystal shows enhanced transport properties, with carrier mobility increased to 2.512 × 103 cm2/(V•s) and resistivity reduced to 0.521 × 10−3 ohm•cm.

Chemical interaction of InAs, InSb, GaAs, and GaSb crystals with aqueous (NH4)2Cr2O7–HBr solutions

We have studied the nature and kinetics of the chemical interaction of InAs, InSb, GaAs, and GaSb crystals with aqueous (NH4)2Cr2O7–HBr solutions. The dissolution rate of the crystals has been measured as a function of etchant composition, solution stirring rate, and temperature. The results demonstrate that the dissolution rate of the semiconductors is diffusion-limited. We have determined the composition ranges of polishing solutions, optimized their compositions, and found conditions for the dynamic chemical polishing of the semiconductors. Ultrasmooth polished semiconductor surfaces have been obtained, with R a ≈ 1 nm.

High-Mobility GaSb Nanostructures Cointegrated with InAs on Si

GaSb nanostructures integrated on Si substrates are of high interest for p-type transistors and mid-IR photodetectors. Here, we investigate the metalorganic chemical vapor deposition and properties of GaSb nanostructures monolithically integrated onto silicon-on-insulator wafers using template-assisted selective epitaxy. A high degree of morphological control allows for GaSb nanostructures with critical dimensions down to 20 nm. Detailed investigation of growth parameters reveals that the GaSb growth rate is governed by the desorption processes of an Sb surface layer and, in turn, is insensitive to changes in material transport efficiency. The GaSb crystal structure is typically zinc-blende with a low density of rotational twin defects, and even occasional twin-free structures are observed. Hall/van der Pauw measurements are conducted on 20 nm-thick GaSb nanostructures, revealing high hole mobility of 760 cm2/(V s), which matches literature values for high-quality bulk GaSb crystals. Finally, we demonstrate a process that enables cointegration of GaSb and InAs nanostructures in close vicinity on Si, a preferred material combination ideally suited for high-performance complementary III-V metal-oxide-semiconductor technology.

GaSb和GaInSb晶体制备工艺研究进展

GaSb和GaInSb晶体制备工艺研究进展

Structural, optical and electrical characterization of InAs0.83Sb0.17 p-π-n photodetector grown on GaAs substrate

High quality InAs0.83Sb0.17 mid-wavelength infrared p-π-n photodetector structure was grown with the aid of a GaSb transition layer on semi-insulating GaAs substrate by molecular beam epitaxy. The lattice mismatch and the crystal quality of the structure were investigated by high resolution X-ray diffraction rocking curve measurement. The full width at half maximum values for InAs0.83Sb0.17 and GaSb crystals were determined as 215 and 238arcsec, respectively. The lattice mismatch between InAs0.83Sb0.17/GaSb structure and GaAs substrate was identified as 8.44%. Activation energies for two different temperature regimes were extracted from Arrhenius plot which was derived from temperature dependent dark current measurements. The dominant dark current mechanisms were determined as generation-recombination limited and surface leakage based for higher- and lower-temperature regimes, respectively. The cut off wavelength and the peak quantum efficiency of the photodetector were obtained from the spectral photoresponse as 4.23μm and 24.3% at 80K, respectively.

Growth of High Material Quality Group III-Antimonide Semiconductor Nanowires by a Naturally Cooling Process.

We report on a simple but powerful approach to grow high material quality InSb and GaSb nanowires in a commonly used tube furnace setup. The approach employs a process of stable heating at a high temperature and then cooling down naturally to room temperature with the nanowire growth occurred effectively during the naturally cooling step. As-grown nanowires are analyzed using a scanning electron microscope and a transmission electron microscope equipped with an energy-dispersive X-ray spectroscopy setup. It is shown that the grown nanowires are several micrometers in lengths and are zincblende InSb and GaSb crystals. The FET devices are also fabricated with the grown nanowires and investigated. It is shown that the grown nanowires show good, desired electrical properties and should have potential applications in the future nanoelectronics and infrared optoelectronics.