The objective of this work is to develop molecular beam epitaxy (MBE) technology of InAs/GaSb type-II superlattices (T2SLs) on GaSb substrates for mid-infrared photodetectors. There are three major challenges in growing high quality T2SLs. First, to obtain an oxide-free and smooth GaSb surface for the growth of GaSb buffer layer. Second, to compensate the mismatch (0.6 %) in lattice constant between InAs and GaSb for minimal residual strain in the sample. Third, to maintain a sharp arsenide/antimonide hetero-interface throughout the entire T2SL, which typically has 100 or more periods, for high optical quantum yield.
The mini-bands of InAs/GaSb superlattices are also investigated by simulated. The simulation results show that the transition energy between the mini-bands in the conduction band and valence band is mainly determined by the thickness of the InAs layer. Increase the thickness of InAs layer from 4 ML to 10 ML, the transition shows a wavelength red shift from 2.4 μm to 4.9 μm. The InSb strain compensation layer plays a minor role because its thickness is less than 1 ML in the samples of interest. The difference in the simulated and experimental transition energies is within 3 %.
In this study, T2SLs with 77 K luminescence at 2.8 μm, 2.9 μm, and 4.1 μm have been grown on GaSb. GaSb buffer with a full width at half maximum (FWHM) of the x-ray diffraction (XRD) rocking curve as low as 15.7 arcsec has been achieved. The tensile strain in InAs is successfully compensated by inserting an InSb layer in the middle of InAs/GaSb interfaces. A residual strain less than 0.1 % is achieved as evidenced by XRD analysis. Using arsenic tetramer (As4) instead of dimer (As2) for the growth of InAs to avoid arsenide/antimonide intermixing, T2SLs with a 77 K photoluminescence (PL) linewidth of 30 meV are obtained. The XRD (-1) satellite peak exhibits a linewidth of 40 arcsec, confirming the abruptness of the heterointerface.

The objective of this work is to develop molecular beam epitaxy (MBE) technology of InAs/GaSb type-II superlattices (T2SLs) on GaSb substrates for mid-infrared photodetectors. There are three major challenges in growing high quality T2SLs. First, to obtain an oxide-free and smooth GaSb surface for the growth of GaSb buffer layer. Second, to compensate the mismatch (0.6 %) in lattice constant between InAs and GaSb for minimal residual strain in the sample. Third, to maintain a sharp arsenide/antimonide hetero-interface throughout the entire T2SL, which typically has 100 or more periods, for high optical quantum yield.
The mini-bands of InAs/GaSb superlattices are also investigated by simulated. The simulation results show that the transition energy between the mini-bands in the conduction band and valence band is mainly determined by the thickness of the InAs layer. Increase the thickness of InAs layer from 4 ML to 10 ML, the transition shows a wavelength red shift from 2.4 μm to 4.9 μm. The InSb strain compensation layer plays a minor role because its thickness is less than 1 ML in the samples of interest. The difference in the simulated and experimental transition energies is within 3 %.
In this study, T2SLs with 77 K luminescence at 2.8 μm, 2.9 μm, and 4.1 μm have been grown on GaSb. GaSb buffer with a full width at half maximum (FWHM) of the x-ray diffraction (XRD) rocking curve as low as 15.7 arcsec has been achieved. The tensile strain in InAs is successfully compensated by inserting an InSb layer in the middle of InAs/GaSb interfaces. A residual strain less than 0.1 % is achieved as evidenced by XRD analysis. Using arsenic tetramer (As4) instead of dimer (As2) for the growth of InAs to avoid arsenide/antimonide intermixing, T2SLs with a 77 K photoluminescence (PL) linewidth of 30 meV are obtained. The XRD (-1) satellite peak exhibits a linewidth of 40 arcsec, confirming the abruptness of the heterointerface.

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