2020年1月20日星期一

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.

Source:IOPscience

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2020年1月13日星期一

Below bandgap optical absorption in tellurium-doped GaSb

Enhancement in below bandgap room temperature infrared transmission has been observed in tellurium (Te)-doped GaSb bulk crystals. The effect of Te concentration on the transmission characteristics of GaSb has been experimentally and theoretically analysed. Undoped GaSb is known to exhibit p-type conductivity with residual hole concentration of the order of (1–2) × 1017 cm−3 at room temperature due to the formation of native defects. For such samples, inter-valence band absorption has been found to be the dominant absorption mechanism. The residual holes could be compensated by n-type dopants such as Te. With increasing Te concentration, free carrier absorption due to electrons and inter-valley transitions in the conduction subband become significant. The dependences of various absorption mechanisms as a function of wavelength have been discussed in this paper.

Source:IOPscience

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2020年1月7日星期二

Room Temperature CW Operation of GaSb/AlGaSb MQW Laser Diodes Grown by MBE

CW operation was achieved by a mesa-stripe (10 µm wide and 200 µm long) GaSb(12 nm)/Al0.35Ga0.65Sb(3 nm) modified multi-quantum-well (MQW, 6 wells) laser diode grown by molecular beam epitaxy (MBE) with threshold current Ith=145 mA at 14°C. Lasing wavelength was 1.662 µm at 9°C. Keys to this achievement were optimizations in (i) MBE growth condition, (ii) layer structure of the MQW wafer (introduction of a superlattice buffer layer and high barrier layers in MQW), and (iii) device fabrication processes. This is the first realization of room temperature cw operation among any type of laser diodes made from an Al-Ga-Sb material system.

Source:IOPscience

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H 2 O 2 :  HF  :  C 4 O 6 H 6    ( Tartaric Acid )  :  H 2 O  Etching System for Chemical Polishing of GaSb

We present the results of a study of  solution for chemical polishing of  wafers. The influence of etching solution composition on surface morphology was studied. The solutions investigated varied in  (2.0–3.0 mol) and (0.0–5.0 mol) concentrations, but contained a constant concentration of tartaric acid (0.7 mol). It was found that the etchant has excellent polishing properties for  wafers when the  concentration was less than 1.5 mol. For  concentration larger than 1.5, the etchant solution produced rough surfaces. The dependencies of the etching rate on solution composition, temperature, and etching time were studied.

Source:IOPscience

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