Self-formation of InAs/InGaAsSb type-II superlattice structures on InP substrates by MBE and their application to mid-infrared LEDs

InAs/InGaAsSb type-II superlattice structures (SLSs) were spontaneously formed by the molecular beam epitaxy of InAs/GaAs0.86Sb0.14 SLSs on InP substrates. The strain due to lattice mismatch between InAs and GaAs0.86Sb0.14 induced two exchange reactions of In–Ga and As–Sb at both InAs/GaAs0.86Sb0.14 heterointerfaces, resulting in the strain relaxation and the self-formation of InAs/InGaAsSb type-II SLS. By energy dispersive x-ray spectroscopy analysis, the mixed crystal composition of the InGaAsSb layer was determined to be approximately In0.8Ga0.2As0.9Sb0.1. Electroluminescence spectra of LEDs, including the self-formed InAs/In0.8Ga0.2As0.9Sb0.1 2.5-periodic SLS, showed double peaks of 2.6 and 3.2 µm at 15 K. The luminescence spectrum was based on two transition mechanisms of type-I transition in InAs and type-II transition between InAs and InGaAsSb. The experimental results of luminescence spectra were supported by theoretical calculations. The 3.3 µm emission was maintained above 220 K.