Asymmetric and symmetric interfaces in type II MWIR InAs/GaSb superlattices

Abstract

We report on the comprehensive investigations of InAs/GaSb type-II superlattice (SL) with asymmetric and symmetric interfaces (IFs) formed using a migration-enhanced epitaxy (MEE) and an interrupted growth. The best structural and optical properties were observed for strain-balanced SL with asymmetric IFs grown using MEE at the bottom IF and continuous growth at the upper IF. The analysis of IF-related lines in Raman spectra of investigated SLs allowed for the evaluation of the quality of the InSb-like and GaAs-like interfaces. The thermal dependency of band gap energy was established from photoluminescence measurements according to the Varshni formula. The activation energies E1 and E2 for the dual-channel non-radiative recombination process were calculated. Linear characteristics of PL intensity vs. excitation power density were fitted using the relation IPL ∼ Eexck with different k. This allowed for the indication of dominant recombination mechanisms: radiative with a share of Auger process (k ≈ 0.8), pure radiative (k ≈ 1.0), and radiative with a slight share of Shockley–Read–Hall (k ≈ 1.1). Different behaviours of PL peak energy depending on the increase of excitation power density were observed: it was either blue-shifted, red-shifted, and/or a combination of both.