Temperature dependence of diffusion length and mobility in mid-wavelength InAs/InAsSb superlattice infrared detectors

Abstract

In the past decade, infrared detectors with InAs/InAsSb (Gallium-free) type-II strained layer superlattice absorbers became a technology of interest for many imaging applications. In this work, we study the dependence of minority carrier (hole) transport, absorption coefficient, and quantum efficiency (QE) of a 5.6 μm cutoff wavelength mid-wavelength infrared InAs/InAsSb detector on temperatures and applied bias. We found that the minority carrier lifetime is very long (τ ≈ 5.5 μs) and is temperature independent in the temperature range T = 50–150 K. The back-side illuminated QE without anti-reflection coating increases from ∼30% at T = 50 K to ∼60% at T = 180 K. The minority carrier (hole) diffusion length, Ldh, was found from QE and absorption coefficient. The hole diffusion length at T = 50 K is Ldh = 2.4 μm and increases monotonically to Ldh = 7.2 μm at T = 180 K. The hole mobility, calculated from diffusion length and minority carrier lifetime, is μh = 4.5 cm2/V s at T = 50 K and increases with temperature to reach μh = 7.2 cm2/V s at T = 150 K. In addition, we find that at lower temperatures where the diffusion length is shorter, the stronger QE dependence on applied bias is due to minority carrier collection from the depletion region, whose width increases with applied bias.