Defects in MBE-grown In AsXSb1-X strained layer superlattices

Abstract

III-V alloy devices are being considered for applications as infrared detectors, by several research groups due to processing advantages over II-VI alloy devices. InAs0.4Sb0.6 has the lowest band gap at 77 K among all III-V compounds, which corresponds to a cut off wavelength of 9 μm. The use of strained layer superlattices (SLS) was first proposed by Osbourn for lowering the band gap and achieving absorption at wavelengths greater than 12 μm at 77 K. A schematic diagram of the device is shown in figure 1. It was grown by Molecular Beam Epitaxy (MBE) at 425 °C and it consists of a p-n junction embedded in a InAs0.15Sb0.85/InSb SLS with layers of equal (110 Å) thickness. The n and p type dopants were S (PbS) and Be respectively. The active device SLS was grown on a composition graded strain relief buffer on the (100) face of an InSb substrate. The samples were sliced, thinned, polished, dimpled and ion milled for making cross-section Transmission Electron Microscope (TEM) samples.