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The objective of this work is to establish molecular beam epitaxy (MBE) growth processes that can produce high
quality InAs/GaInSb superlattice (SL) materials specifically tailored for very long wavelength infrared (VLWIR)
detection. To accomplish this goal, several series of MBE growth optimization studies, using a SL structure of 47.0 Å
InAs/21.5 Å Ga0.75In0.25Sb, were performed to refine the MBE growth process and optimize growth parameters.
Experimental results demonstrated that our “slow” MBE growth process can consistently produce an energy gap near 50
meV. This is an important factor in narrow band gap SLs. However, there are other growth factors that also impact the
electrical and optical properties of the SL materials. The SL layers are particularly sensitive to the anion incorporation
condition formed during the surface reconstruction process. Since antisite defects are potentially responsible for the
inherent residual carrier concentrations and short carrier lifetimes, the optimization of anion incorporation conditions, by
manipulating anion fluxes, anion species, and deposition temperature, was systematically studied. Optimization results
are reported in the context of comparative studies on the influence of the growth temperature on the crystal structural
quality and surface roughness performed under a designed set of deposition conditions. The optimized SL samples
produced an overall strong photoresponse signal with a relatively sharp band edge that is essential for developing
VLWIR detectors. A quantitative analysis of the lattice strain, performed at the atomic scale by aberration corrected
transmission electron microscopy, provided valuable information about the strain distribution at the GaInSb-on-InAs
interface and in the InAs layers, which was important for optimizing the anion conditions.
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