Investigation of Trap States in Mid-Wavelength Infrared Type II Superlattices Using Time-Resolved Photoluminescence

Abstract

Time-resolved photoluminescence (TRPL) spectroscopy is used to study the minority-carrier lifetime in mid-wavelength infrared, n-type, InAs/Ga1−x In x Sb type II superlattices (T2SLs) and investigate the recombination mechanisms and trap states that currently limit their performance. Observation of multiple exponential decays in the intensity-dependent TRPL data indicates trap saturation due to the filling then emptying of trap states and different Shockley–Read–Hall (SRH) lifetimes for minority and majority carriers, with τ maj (τ n0) ≫ τ min (τ p0). Simulation of the photoluminescence transient captures the qualitative behavior of the TRPL data as a function of temperature and excess carrier density. A trap state native to Ga1−x In x Sb is identified from the low-injection temperature-dependent TRPL data and found to be located below the intrinsic Fermi level of the superlattice, approximately 60 ± 15 meV above the valence-band maximum. Low-temperature TRPL data show a variation of the minority-carrier SRH lifetime, τ p0, over a set of InAs/Ga1−x In x Sb T2SLs, where τ p0 increases as x is varied from 0.04 to 0.065 and the relative layer thickness of Ga1−x In x Sb is increased by 31%.