## 2019年12月25日星期三

### Acceptor Densities and Acceptor Levels in Undoped GaSb Determined by Free Carrier Concentration Spectroscopy

Without any assumptions regarding residual impurity species in an undoped semiconductor, it is experimentally demonstrated that the densities and energy levels of impurities can be precisely determined by the graphical peak analysis method based on Hall-effect measurements, referred to as free carrier concentration spectroscopy (FCCS). Using p-type undoped GaSb epilayers grown by molecular beam epitaxy (MBE), the densities and energy levels of several acceptor species are accurately determined. Five acceptor species are detected in the undoped GaSb epilayers grown by MBE, while two are also found in p-type undoped GaSb wafers. A 21–41 meV acceptor and a 75–99 meV acceptor exist both in the epilayers and in the wafer. On the other hand, a 164–181 meV acceptor is detected in epilayers grown at an Sb4/Ga flux beam equivalent pressure ratio of 8 or 10, while a 259 meV acceptor is found in the epilayer grown at Sb4/Ga = 6. In addition, a very shallow acceptor, which is completely ionized at 80 K, is found in the epilayers. The densities of the very shallow acceptor and the 21–41 meV acceptor are minimum at Sb4/Ga = 8, which makes the hole concentration lowest in the temperature range of the measurement.

Source:IOPscience

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## 2019年12月18日星期三

### 2.2–2.7 μm side wall corrugated index coupled distributed feedback GaSb based laser diodes

We report on the modeling, growth, processing, characterization and integration in a gas detection setup of side wall corrugated distributed feed-back antimonide diode lasers emitting at 2.28 and 2.67 μm. The laser structures were grown by molecular beam epitaxy on GaSb substrate. Ridge lasers were fabricated from the grown wafers according to the following process: a second order Bragg grating was defined on the sides of the ridges by interferometric lithography, optical lithography and etched in a Cl-based inductively coupled plasma reactor. The devices exhibit a power reaching 40 mW, a side mode suppression ratio better than 28 dB and a tuning range of 3 nm at room temperature. One of these devices was successfully integrated in a tunable diode laser absorption spectroscopy setup, thus demonstrating that they are suitable for gas analysis.

Source:IOPscience
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### Room Temperature Bonding of Wafers Using Si and Ge Films with Extremely Low Electrical Conductivity

The technical potential of room temperature bonding of wafers in vacuum using amorphous Si (a-Si) and Ge (a-Ge) films was studied. Transmission electron microscopy images revealed no interface corresponding to the original films surfaces for bonded a–Ge–a–Ge films. Analyses of film structure and the surface free energy at the bonded interface revealed higher bonding potential at the connected a–Ge–a–Ge interface than that of a–Si films. The electrical resistivity of a-Ge films is 0.62 Ωm, which is lower than that of a-Si film (4.7 Ωm), but 7–8 order higher than that of representative material films used for bonding in vacuum. Our results indicate that room temperature bonding using a–Ge films is useful to bond wafers without any marked influence on the electrical properties of devices on wafer surfaces caused by the electrical conductivity of films used for bonding.

Source:IOPscience
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## 2019年12月12日星期四

### Investigation of a near mid-gap trap energy level in mid-wavelength infrared InAs/GaSb type-II superlattices

In this report, we present results of an experimental investigation of a near mid-gap trap energy level in InAs10 ML/GaSb10 ML type-II superlattices. Using thermal analysis of dark current, Fourier transform photoluminescence and low-frequency noise spectroscopy, we have examined several wafers and diodes with similar period design and the same macroscopic construction. All characterization techniques gave nearly the same value of about 140 meV independent of substrate type. Additionally, photoluminescence spectra show that the transition related to the trap centre is temperature independent. The presented methodology for thermal analysis of dark current characteristics should be useful to easily estimate the position of deep energy levels in superlattice photodiodes.

Source:IOPscience

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## 2019年12月4日星期三

### Molecular beam epitaxy of interband cascade structures with InAs/GaSb superlattice absorbers for long-wavelength infrared detection

The interfaces of InAs/GaSb superlattices (SLs) were studied with the goal of improving interband cascade infrared photodetectors (ICIPs) designed for the long-wavelength infrared region. Two ICIP structures with different SL interfaces were grown by molecular beam epitaxy, one with a ~1.2 monolayer (ML) InSb layer inserted intentionally only at the GaSb-on-InAs interfaces and another with a ~0.6 ML InSb layer inserted at both InAs-on-GaSb and GaSb-on-InAs interfaces. The material quality of the ICIP structures was similar according to characterization by differential interference contrast microscopy, atomic force microscopy, and x-ray diffraction. The performances of the ICIP devices were not substantially different despite the different interface structure. Both ICIPs had a peak detectivity of >3.7 × 1010 Jones at 78 K with a cutoff wavelength near 9.2 μm. The maximum operation temperatures of both ICIPs were as high as ~250 K, although the structures were not fully optimized. This suggests that the two interface arrangements may have a similar effect on structural, optical and electrical properties. Alternatively, the device performance of the ICIPs may be limited by mechanisms unrelated to the interfaces. In either case, the arrangement of dividing a thick continuous InSb layer at the GaSb-on-InAs interface into thinner InSb layers at both interfaces can be used to achieve strain balance in SL detectors for longer wavelengths. This suggests that with further improvements ICIPs should be able to operate at higher temperatures at even longer wavelengths.

Source:IOPscience

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## 2019年11月27日星期三

### Reflectivity modulator based on GaSb/GaAs heterostructure

A structure of gallium antimonide (GaSb) and gallium arsenide (GaAs) wafers is built to modulate light reflectivity at CO2 laser wavelength. A quantum well composed of GaSb/GaAs heterojunction with highly doped GaAs up to 3×1018 cm-3 is inserted inside a layer structure. A grating of periodic structure of GaAs and gold layer is added just below the substrate. Gsolver software is used to determine the reflectivity of incident light with the existence of free carriers. A voltage is applied to the doped layer to deplete the free electrons and the reflectivity is determined again. The significant difference in reflectivity between the two cases can be used to build a light reflectivity modulator device.

Source:IOPscience

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## 2019年11月20日星期三

### Interfacial and mechanical characterization of wafer-bonded GaSb/amorphous α-(Ga,As)/GaAs structure for GaSb-on-insulator applications

In this study, the feasibility of using wafer-bonding technology to fabricate a GaSb semiconductor on GaAs substrates for potentially creating a GaSb-on-insulator structure has been demonstrated. A GaSb wafer has been bonded on two types of GaAs substrates: (1) a regular single crystal semi-insulating GaAs substrate and (2) the GaAs wafers with pre-deposited low-temperature amorphous α-(Ga,As) layers. The microstructures and interface adhesion studies have been carried out on these wafer-bonded semiconductors. It has been found that the GaSb-on-α-(Ga,As) wafers have shown enhanced interface adhesion and lower temperature bonding capability.

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## 2019年11月11日星期一

### nvestigation of a near mid-gap trap energy level in mid-wavelength infrared InAs/GaSb type-II superlattices

In this report, we present results of an experimental investigation of a near mid-gap trap energy level in InAs10 ML/GaSb10 ML type-II superlattices. Using thermal analysis of dark current, Fourier transform photoluminescence and low-frequency noise spectroscopy, we have examined several wafers and diodes with similar period design and the same macroscopic construction. All characterization techniques gave nearly the same value of about 140 meV independent of substrate type. Additionally, photoluminescence spectra show that the transition related to the trap centre is temperature independent. The presented methodology for thermal analysis of dark current characteristics should be useful to easily estimate the position of deep energy levels in superlattice photodiodes.

Source:IOPscience

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## 2019年11月6日星期三

### Thermophotovoltaic furnace–generator for the home using low bandgap GaSb cells

It is well known that distributed combined heat and power (CHP) systems for commercial and industrial buildings are economically desirable because they conserve energy. Here, a thermophotovoltaic (TPV) unit is described that brings CHP into the home providing both heat and electric power by replacing the typical home heating furnace with a combined TPV furnace–generator. First, the design of a 1.5 kWelectric/12.2 kWthermal TPV furnace–generator is described along with the key components that make it possible. Diffused junction GaSb cells are one of these key components. Secondly, an economic cost target is determined for this system where the cost of the photovoltaic array will be key to the economical implementation of this concept. Finally, it is argued that the GaSb cells and arrays can be manufactured at the required low cost. The cost target can be reached because the GaSb cells in the TPV furnace–generator can produce an electrical power density of 1 W cm−2 which is 100 times higher than the typical solar cell. The cost target can also be reached because the GaSb cell fabrication process parallels the silicon solar cell process where no toxic gases are used, no wafer polish is required and cast polycrystalline cells can be used.

Source:IOPscience

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## 2019年10月30日星期三

### Wafer-scale processing technology for monolithically integrated GaSb thermophotovoltaic device array on semi-insulating GaAs substrate

This paper presents the entire fabrication and processing steps necessary for wafer scale monolithic integration of series interconnected GaSb devices grown on semi-insulating GaAs substrates. A device array has been fabricated on complete 50 mm (2 inch) diameter wafer using standard photolithography, wet chemical selective etching, dielectric deposition and single-sided metallization. For proof of concept of the wafer-scale feasibility of this process, six large-area series interconnected GaSb p–n junction thermophotovoltaic cells with each cell consisting of 24 small-area devices have been fabricated and characterized for its electrical connectivity. The fabrication process presented in this paper can be used for optoelectronic and electronic device technologies based on GaSb and related antimonide based compound semiconductors.

Source:IOPscience

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## 2019年8月21日星期三

### An investigation of the crystalline nature for GaSb films on Si(111) at varied growth temperature and growth rate

The single crystalline III-V films on substrates such as silicon and germanium are preferred by researchers to enhance the performance of a MOSFET or CMOS. In this study, we investigated the possible factors responsible for generating twin crystal growth for III-antimonides, especially GaSb grown on Si(111). We tested several base templates such as Si(111)-3 × 3-Ga, Si(111)-3 × 3-In, Si(111)-direct, and we have varied the growth conditions through varying the substrate temperature and growth rate. The molecular beam epitaxy growth method was used to deposit GaSb films. Our results reflect that in absence of an initial layer of GaSb film grown at a low substrate temperature, the anti-phase domains and defect densities cannot be reduced which results in the formation of twin crystal. We found that the high substrate temperature during the growth is the deciding factor in generating twin crystal growth.

Source:IOPscience

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## 2019年8月16日星期五

### Study of hydrogen implantation-induced blistering in GaSb for potential layer transfer applications

GaSb samples were implanted by 100 keV hydrogen ions (H+) at room temperature with fluence values of 1  ×  1017 and 2  ×  1017 ions cm−2. Post-implantation annealing studies revealed that the samples implanted with a fluence of 2  ×  1017 ions cm−2 did not show blistering/exfoliation. For the lower fluence, the samples showed the formation of surface blisters/craters along with the large area exfoliation of the top H-implanted surface. Topographical investigations of the samples were carried out using Nomarski optical microscopy, atomic force microscopy and stylus surface profilometry. The lateral sizes and heights of the blisters varied between 2–5 µm and 5–20 nm respectively. The root mean square roughness of the exfoliated region was about 12 nm while the exfoliation depth was found to be 730 nm. The exfoliation depth in the H-implanted GaSb is close to the damage concentration peak as found from SRIM calculations. The Föppl–von Karman theory of thin plates has been used to understand the effect of internal pressure and stress on the surface blistering. Using the above mentioned implantation and annealing parameters, potential layer transfer of GaSb could be enabled.

Source:IOPscience

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## 2019年8月9日星期五

### X-ray scattering from epitaxial GaSb/InAs thin films below and above the critical thickness

The structure of layers of GaSb grown on InAs substrates has been investigated by means of high-resolution x-ray diffraction. The samples were grown in Oxford using the metal–organic vapour phase epitaxy facility to produce high-quality single-crystal layers with thicknesses between 60 and 3000 Å. The x-ray scattering experiments were performed with a Philips MRD diffractometer in Oxford and with the XMaS facility at the ESRF. The results show that the scattering for layers with a thickness below Tc' ~ 1250 Å is different from the scattering for those with larger thicknesses. The scattering from the thinner layers shows that the in-plane lattice constant of the GaSb is very close to that of the InAs substrate and that the strain does not vary through the film, while the measured diffuse scattering is in good agreement with calculations of the scattering from isolated 60o dislocations. The thicker layers show no diffuse scattering but single-Gaussian Bragg peaks and the scattering is that expected from a mosaic layer with a large concentration of 60o dislocations. Analysis of the peak parameters shows that the average in-plane lattice constant is intermediate between those of bulk GaSb and bulk InAs and that there is a changing strain through the film. The critical thickness Tc for GaSb on InAs is calculated as about 204 Å. We argue that between 204 and 1250 Å there are only a few dislocations, but thicker films are relaxed by spontaneous creation of a dislocation network. The results demonstrate the power of high-resolution x-ray scattering for studying non-destructively the structures of thin films containing dislocations, and show that there is a marked change in the scattering for layers above the critical thicknesses Tc and Tc'.

Source:IOPscience

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## 2019年8月1日星期四

### Growth of self-assembled PbSe quantum-dots on GaSb(100) by liquid phase epitaxy

Self-assembled PbSe quantum-dots (QD) have been grown on GaSb(100) substrates from the liquid phase. A Pb-rich melt at 517°C was used with 10°C supercooling and with a short (10 ms) melt-substrate contact time. Atomic force microscopy has revealed that the PbSe QDs are 4–10 nm in height and 10–40 nm in diameter, with an area density of 1.7×1010 cm−2. The growth of QDs occurs in the Volmer–Weber mode and is a result of the difference in lattice structures between the PbSe and GaSb rather than the lattice constants.

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## 2019年7月23日星期二

### A review on MBE-grown HgCdSe infrared materials on GaSb (211)B substrates

We review our recent efforts on developing HgCdSe infrared materials on GaSb substrates via molecular beam epitaxy (MBE) for fabricating next generation infrared detectors with features of lower production cost and larger focal plane array format size. In order to achieve high-quality HgCdSe epilayers, ZnTe buffer layers are grown before growing HgCdSe, and the study of misfit strain in ZnTe buffer layers shows that the thickness of ZnTe buffer layer needs to be below 300 nm in order to minimize the generation of misfit dislocations. The cut-off wavelength/alloy composition of HgCdSe materials can be varied in a wide range by varying the ratio of Se/Cd beam equivalent pressure during the HgCdSe growth. Growth temperature presents significant impact on the material quality of HgCdSe, and lower growth temperature leads to higher material quality for HgCdSe. Typically, long-wave infrared HgCdSe (x=0.18, cut-off wavelength of  at 80 K) presents an electron mobility as high as , a background electron concentration as low as 1.6×1016 cm−3, and a minority carrier lifetime as long as . These values of electron mobility and minority carrier lifetime represent a significant improvement on previous studies of MBE-grown HgCdSe reported in the open literatures, and are comparable to those of counterpart HgCdTe materials grown on lattice-matched CdZnTe substrates. These results indicate that HgCdSe grown at the University of Western Australia, especially long-wave infrared can meet the basic material quality requirements for making high performance infrared detectors although further effort is required to control the background electron concentration to below 1015 cm−3. More importantly, even higher quality HgCdSe materials on GaSb are expected by further optimizing the growth conditions, using higher purity Se source material, and implementing post-growth thermal annealing and defect/impurity gettering/filtering. Our results demonstrate the great potential of HgCdSe infrared materials grown on GaSb substrates for fabricating next generation infrared detectors with features of lower cost and larger array format size.

Source:IOPscience

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## 2019年7月17日星期三

### Investigation of GaSb epilayer grown on vicinal GaAs(001) substrate by high resolution x-ray diffraction

GaSb epilayers grown on GaAs(001) vicinal substrate misoriented towards (111) plane were studied using high-resolution x-ray diffraction (HRXRD). The results show that GaSb epilayers exhibit positive crystallographic tilt and the distribution of 60° misfit dislocations (MDs) is imbalanced. The vicinal substrate also leads to the anisotropy of the mosaic structure, i.e. the lateral coherent lengths in [1\bar 10] directions are larger than those in [110] directions. Furthermore, the full-width at half maximum (FWHM) of the off-axis peaks varies with the inclination angle, which is a result of different dislocation densities in the \{111\} glide planes.

Source:IOPscience

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## 2019年7月9日星期二

### Selective area heteroepitaxy of GaSb on GaAs (001) for in-plane InAs nanowire achievement

The growth of in-plane GaSb nanotemplates on a GaAs (001) substrate is demonstrated combining nanoscale patterning of the substrate and selective area heteroepitaxy. The selective growth of GaSb inside nano-stripe openings in a SiO2 mask layer is achieved at low temperature thanks to the use of an atomic hydrogen flux during the molecular beam epitaxy. These growth conditions promote the spreading of GaSb inside the apertures and lattice mismatch accommodation via the formation of a regular array of misfit dislocations at the interface between GaSb and GaAs. We highlight the impact of the nano-stripe orientation as well as the role of the Sb/Ga flux ratio on the strain relaxation of GaSb along the [110] direction and on the nanowire length along the [1-10] one. Finally we demonstrate how these GaSb nanotemplates can be used as pedestals for subsequent growth of in-plane InAs nanowires.

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## 2019年7月5日星期五

### The growth of n-type GaSb by metal-organic chemical vapour deposition: effects of two-band conduction on carrier concentrations and donor activation

n-type GaSb has been prepared by metal-organic chemical vapour deposition with tellurium donors using diethyltelluride as the dopant precursor. The maximum carrier concentration achieved was 1.7 × 1018 cm−3, as measured by van der Pauw–Hall effect measurements, for an atomic tellurium concentration of 1.8 × 1019 cm−3. The apparent low activation of tellurium donors is explained by a model that considers the effect of electrons occupying both the Γ and L bands in GaSb due to the small energy difference between the Γ and L conduction band minima. The model also accounts for the apparent increase in the carrier concentration determined by van der Pauw–Hall effect measurements at cryogenic temperatures.

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## 2019年6月20日星期四

### Strain Accommodation in GaSb/AlSb Superlattices on (001) GaSb Substrates with AlSb Buffers

We report the observation that AlSb layers thinner than the epilayer critical thickness for the onset of plastic relaxation undergo lattice relaxation when used as buffers for GaSb/AlSb superlattices on (001) GaSb substrates. It is found that this is induced by the external stress from the overlaying superlattice, and that the mechanism is consistent with relaxation processes involving the nucleation and expansion of half-loops earlier suggested for strained epilayers. Photoluminescence spectroscopy conforms with the in-plane strains calculated from double-crystal and small-angle X-ray diffraction measurements.

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## 2019年6月14日星期五

### Multiple-scattering effects in Ga K-edge extended x-ray absorption fine structure spectra of GaP, GaAs and GaSb semiconductor compounds

The dependence of Ga K-edge multiple-scattering extended x-ray absorption fine structure (MS-EXAFS) effects on the nearest neighbours in GaP, GaAs and GaSb semiconductor compounds with the zinc blende structure has been comprehensively investigated by considering the coordination environment within the first three shells around the Ga atoms. It is revealed that in the case of GaP with a light element as the first neighbour of the Ga absorber, the MS-EXAFS effects are negligibly weak with respect to the single-scattering (SS) contribution. For GaAs and GaSb compounds with heavier elements as the first neighbour of the Ga absorber, the MS effects become increasingly important and are dominated by a triangular double-scattering path DS2 (\mathrm {Ga}_{0} \to \mathrm {B}_{1} \to \mathrm {B}_{2} \to \mathrm {Ga}_{0} ). The EXAFS contribution of the DS2 path destructively interferes with that of the second shell single-scattering path (SS2), with the amplitude ratio of DS2 to SS2 rising from 7% for GaP to 25 and 70% for GaAs and GaSb, respectively. This indicates that the second shell peak magnitude for these compounds is increasingly damped by the MS effects as the first nearest neighbour goes from P to Sb. Based on these results, we present a generalized and simplified high-shell MS-EXAFS analysis method for compounds with the open structure of zinc blende.

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## 2019年6月5日星期三

### High-crystalline GaSb epitaxial films grown on GaAs(001) substrates by low-pressure metal–organic chemical vapor deposition

Orthogonal experiments of GaSb films growth on GaAs(001) substrates have been designed and performed by using a low-pressure metal–organic chemical vapor deposition (LP-MOCVD) system. The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters. It was demonstrated that the optimized GaSb thin film has a narrow full width at half maximum (358 arc sec) of the (004) ω-rocking curve, and a smooth surface with a low root-mean-square roughness of about 6 nm, which is typical in the case of the heteroepitaxial single-crystal films. In addition, we studied the effects of layer thickness of GaSb thin film on the density of dislocations by Raman spectra. It is believed that our research can provide valuable information for the fabrication of high-crystalline GaSb films and can promote the integration probability of mid-infrared devices fabricated on mainstream performance electronic devices.

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## 2019年5月28日星期二

### Defect properties of as-grown and electron-irradiated Te-doped GaSb studied by positron annihilation

Defects in as-grown undoped and tellurium-doped gallium antimonide were studied using positron lifetime and coincidence Doppler broadening measurements. The grown-in defects in these samples were supposed to be Ga vacancy (VGa)-related defects. More VGa-related defects were introduced into undoped and lightly Te-doped GaSb after electron irradiation at the doses of 1.0 × 1017 cm−2 and 1.0 × 1018 cm−2; however, in the heavily Te-doped GaSb, electron irradiation led to partial recovery of VGa. The role of Te content in the defect evolution is also discussed.

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## 2019年5月23日星期四

### Structural and optical characterization of GaSb on Si (001) grown by Molecular Beam Epitaxy

GaSb epilayers were grown on Si (001) using molecular beam epitaxy via AlSb quantum dots as an interfacial misfit (IMF) array between the Si substrates and GaSb epilayers. The effect of IMF array thickness, growth temperature and post annealing on the surface morphology, structural and optical properties of the GaSb on Si were investigated. Among five different IMF array thicknesses (5, 10, 20, 40 and 80 ML) that were used in this study, the best result was obtained from the sample with a 20 ML AlSb IMF array. Additionally, it was found that although the full width at half maximum (FWHM) and threading dislocation (TD) densities obtained from high resolution x-ray diffraction curves can be improved by increasing the growth temperature, a decrease in the photoluminescence (PL) signal and an increase in the surface roughness (RMS) emerged. On the other hand, the results indicate that by applying post annealing the GaSb epilayer crystal quality can be improved in terms of FWHM, TD density, PL signal or RMS depending on the post annealing temperature. By applying post annealing at 570 °C for 30 min we achieve a FWHM value of 260 arcsec for a 1 μm thick GaSb epilayer on Si (001) and improve the PL signal intensity without worsening the RMS value.

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## 2019年5月9日星期四

### Origin of a localized vibrational mode in a GaSb substrate with a MBE-grown ZnTe epilayer

A localized vibrational mode (LVM) with a remarkable fine structure is observed in the infrared transmission spectrum of a ZnTe epilayer grown with molecular beam epitaxy (MBE) on a GaSb substrate. On the basis of the Zn and Te deposited on the GaSb substrate during the MBE growth of ZnTe, and assuming diffusion of Zn and Te into GaSb, the LVM is attributed to Zn, substitutionally replacing either the cation, Ga (ZnGa), or the anion, Sb (ZnSb). The frequency of the LVM and its fine structure can then be interpreted in terms of the infrared active modes of 64Zn substituting for Sb as an anti-site impurity and treating the centre as an XY4 quasimolecule. With X64Zn and Y69Ga and 71Ga, occupying the nearest-neighbour sites reflecting all the possible combinations and permutations as well as the natural isotopic abundance of Ga, the fine structure of the LVM can be accounted for quantitatively.

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## 2019年4月30日星期二

### Photoluminescene study acceptor defects in lightly doped n type GaSb single crystals

Lightly Te-doped GaSb samples grown by the liquid encapsulated Czochralski (LEC) method have been studied by Hall measurements and low-temperature PL spectroscopy. The results suggest that acceptor-related antisite is the dominant defect in n-type GaSb with low Te-doping concentration. As the Te concentration increases, gallium vacancy related defects become the main acceptor. A new band of around 665 meV is observed in the GaSb sample with the lowest Te-doping concentration. The variation of the acceptor defects and their influence on the electronic and optical property on the n-GaSb single crystal are discussed based on the results.

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## 2019年4月24日星期三

### Anisotropic interface induced formation of Sb nanowires on GaSb(111)A substrates

The growth of Sb nanowires on GaSb(111)A substrates is studied by in situ azimuthal scan reflection high-energy electron diffraction (ARHEED). Bulk and layer contributions can be distinguished in the ARHEED transmission pattern through the Sb nanowires. The three-dimensional structure of the growing Sb nanowires is identified by post-growth atomic force microscopy (AFM) and x-ray diffraction (XRD). The lattice match of the Sb crystal along the $\langle \bar {2}10\rangle$ and the GaSb crystal along $\langle \bar {1}10\rangle$ directions lead to a preferential orientation of the Sb nanowires. The Sb adsorption and desorption kinetics is studied by thermal desorption spectroscopy.

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## 2019年4月18日星期四

### Electrical and optical property of annealed Te-doped GaSb

GaSb is the most suitable substrate in the epitaxial growth of mixed semiconductors of GaSb system. In this work, Te-doped GaSb bulk crystals with different doping concentration have been annealed at 550 °C for 100 h in ambient antimony. The annealed samples have been studied by Hall effect measurement, infrared (IR) optical transmission, Glow discharge mass spectroscopy (GDMS) and photoluminescence (PL) spectroscopy. After annealing, Te-doped GaSb samples exhibit a decrease of carrier concentration and increase of mobility, along with an improvement of below gap IR transmission. Native acceptor related electrical compensation analysis suggests a formation of donor defect with deeper energy level. The mechanism of the variation of the defect and its influence on the material properties are discussed.

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## 2019年4月9日星期二

### Acceptor Densities and Acceptor Levels in Undoped GaSb Determined by Free Carrier Concentration Spectroscopy

Without any assumptions regarding residual impurity species in an undoped semiconductor, it is experimentally demonstrated that the densities and energy levels of impurities can be precisely determined by the graphical peak analysis method based on Hall-effect measurements, referred to as free carrier concentration spectroscopy (FCCS). Using p-type undoped GaSb epilayers grown by molecular beam epitaxy (MBE), the densities and energy levels of several acceptor species are accurately determined. Five acceptor species are detected in the undoped GaSb epilayers grown by MBE, while two are also found in p-type undoped GaSb wafers. A 21–41 meV acceptor and a 75–99 meV acceptor exist both in the epilayers and in the wafer. On the other hand, a 164–181 meV acceptor is detected in epilayers grown at an Sb4/Ga flux beam equivalent pressure ratio of 8 or 10, while a 259 meV acceptor is found in the epilayer grown at Sb4/Ga = 6. In addition, a very shallow acceptor, which is completely ionized at 80 K, is found in the epilayers. The densities of the very shallow acceptor and the 21–41 meV acceptor are minimum at Sb4/Ga = 8, which makes the hole concentration lowest in the temperature range of the measurement.

Source:IOPscience

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## 2019年4月3日星期三

### Mid-infrared InAs/GaSb strained layer superlattice detectors with nBn design grown on a GaAs substrate

We report on a type-II InAs or GaSb strained layer superlattice (SLS) photodetector (λ  ~4.3 µm at 77 K) with nBn design grown on a GaAs substrate using interfacial misfit dislocation arrays to minimize threading dislocations in the active region. At 77 K and 0.1 V of the applied bias, the dark current density was equal to 6 × 10−4 A cm−2 and the maximum specific detectivity D* was estimated to 1.2 × 1011 Jones (at 0 V). At 293 K, the zero-bias D* was found to be ~109 Jones which is comparable to the nBn InAs/GaSb SLS detector grown on the GaSb substrate.

Source:IOPscience

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send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com