Interface roughness estimate from carrier transport in InAs/GaSb superlattices

The performance of infrared focal plane arrays and quantum cascade lasers manufactured from InAs/GaSb type- II superlattices (SLs) depends on the mobility of carriers along the growth axis. In turn, the longitudinal mobility depends on the quality of SL interfaces. In-plane transport is a sensitive measure of interface quality and the degree of interface roughness scattering (IRS). In this paper, we demonstrate the IRS-limited transport regime in InAs/GaSb SL samples grown for this study. We find that the in-plane mobility μ as a function of InAs layer width L behaves as μ ∝ L5 , which closely follows the classic sixth power dependence expected from theory. Fits to the mobility data indicate that, for one monolayer surface roughness, the roughness correlation length is about 35 Å.

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