Abstract
Strained-layer superlattices (SLSs) are an active research topic in the molecular beam epitaxy (MBE) and infrared focal plane array communities. These structures undergo a >500 K temperature change between deposition and operation. As a result, the lattice constants of the substrate and superlattice are expected to change by approximately 0.3%, and at approximately the same rate. However, we present the first temperature-dependent X-ray diffraction (XRD) measurements of SLS material on GaSb and show that the superlattice does not contract in the same manner as the substrate. In both InAs/InAs0.65Sb0.35 and In0.8Ga0.2As/InAs0.65Sb0.35 SLS structures, the apparent out-of-plane strain states of the superlattices switch from tensile at deposition to compressive at operation. These changes have ramifications for material characterization, defect generation, carrier lifetime, and overall device performance of superlattices grown by MBE.
Highlights
Strained layer superlattices (SLSs) are an area of interest for large area infrared focal plane arrays.In comparison to HgCdTe, superlattice superlattice (SLS) structures can be deposited on inexpensive substrates, do not require extensive safety modifications for the deposition of mercury, and can take advantage of commercial foundries
The original structures consisted of InAs/InGaSb [10], which were followed by gallium-free designs (InAs/InAsSb) [1]
The overall performance of SLS-based infrared photodetectors has improved to the point where they have similar dark current (Rule 07) [13] and external quantum efficiency to those based on HgCdTe
Summary
In comparison to HgCdTe, SLS structures can be deposited on inexpensive substrates, do not require extensive safety modifications for the deposition of mercury, and can take advantage of commercial foundries. Multiple academic [1,2,3], industrial [4,5], and government groups [6,7,8,9] have researched these structures using molecular beam epitaxy (MBE). The original structures consisted of InAs/InGaSb [10], which were followed by gallium-free designs (InAs/InAsSb) [1]. Newer versions include InGaAs/InAsSb ternary SLS [11] and InAs/AlAs/AlSb/InAsSb W-structures [6,12]. The overall performance of SLS-based infrared photodetectors has improved to the point where they have similar dark current (Rule 07) [13] and external quantum efficiency to those based on HgCdTe
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