InAs_1-xSb_x has the lowest energy band gap among all the III-V semiconductors and has thus received a great deal of attention as an important material to be incorporated into infrared optoelectronic devices. Photodetectors containing this ternary have potential to reach wavelengths up to 9 µm. To achieve this, high quality thin films with few defects and impurities are required. One of the key issues in using InAs_1-xSb_x in the device architecture (particularly for wavelengths greater than 4 µm) is the lack of available lattice-matched substrates. To date, the best performing InAsSb-containing devices are lattice matched to GaSb substrates, with a 9% antimony solid content. (i.e. InAs_0.91Sb_0.09). This paper focuses on the deposition of high quality thin films of InAs_0.91Sb_0.09 (between 2 µm and 4 µm thick) on 2″ GaSb substrate. The material deposition is performed in a metal organic chemical vapour deposition (MOCVD) system. The process begins by the deposition of a thin (nanometer thickness range) low temperature buffer layer of either GaSb followed by the deposition of strain free InAsSb. High resolution X-ray diffraction (HRXRD) is used to precisely determine the composition of the ternary alloy as well as to investigate the uniformity across the entire wafer. Photoluminescence (PL), using a Fourier-transform infrared (FTIR) spectrometer, is employed to further explore the material quality and purity. Preliminary measurements indicate consistent thickness and compositional uniformity of the InAsSb layers.

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PhD

Prof JR Botha Reinhardt.Botha@nmmu.ac.za NMMU

No

Yes