Study on Inter Band and Inter Sub-Band Optical Transitions With Varying InAs/InGaAs Sub-Monolayer Quantum Dot Heterostructure Stacks Grown by Molecular Beam Epitaxy

Abstract

Multiple stacking of sub-monolayer (SML) quantum dot (QD) heterostructure exhibits high optical quality and is seen in devices like lasers diodes, photodetectors, etc. In this study, we have investigated the optical and material characterization of InAs/InGaAs SML quantum dot (QD) heterostructure with multiple stacking layers (nSML) on GaAs substrates. The experimentally calculated PL emission energies were found to be 1.19, 1.13, 1.11 and 1.12 eV for 4, 6, 8 and 10 QD stacks at 19 K, excitation power of 1.1 kW/cm2 (25 mW) respectively. A feature of increased strain with increasing nSML was verified experimentally by high-resolution X-ray diffraction (HRXRD) and Raman measurements as well. The experimental PL peak energy data were then validated with nextnano++ simulations based on Schrodinger – Poisson device solver. The hydrostatic and biaxial strain components were computed to correlate the experimental and simulation data. Hence with these enunciated understandings, we conclude that an ideal choice on the number of SML stacks that can be grown on a GaAs substrate was found to be 6 stacks, helpful to realize and fabricate QD based infrared photodetectors (QDIPs) devices in long wavelength regime.