Post-growth rapid thermal annealing (RTA): a technological route to achieve high efficient luminescence and reduction of size inhomogeneity in type-II InAs/GaAs(Sb) quantum dots (QDs) Heterostructures for opto-electronic applications

In the current work, impact of ex-situ rapid thermal annealing (RTA) on the optical, structural and crystallographic properties of type-II InAs/GaAs(Sb) QDs heterostructures are investigated in detail. The Stranski–Krastanov (SK) QD heterostructure is grown by using solid-source molecular-beam-epitaxy (MBE) technique with 22% of Sb composition in GaAs(Sb) capping layer. The As-grown (ASG) samples are treated with RTA at temperatures of 750 _°C, 800 _°C, and 850 °C for 30 s under Ar ambient. Temperature dependent and power dependent photoluminescence (TD-PL and PD-PL) measurements are performed to investigate the impact of the emission properties of type-II heterostructures and such annealing induced changes in QD morphology, optical properties and carrier dynamics are remarkably observed due to alloy intermixing in the QD and capping interface region. The 20 K PL peak reveal a strong correlation with the annealing temperature and a strong blueshift (131 nm). The narrow linewidth from 89 nm (ASG) to 32 nm (850 _°C) is found due to an increase in the uniformity of QDs and energy states and their evolution with the RTP temperatures are analysed in detail by using deconvoluted PL peaks. Out-of-plane XRD confirms the slight reduction in hydrostatic strain with the increasing RTA temperature due to the decrease in In-content inside InAs QD. Atomic force microscopy (AFM) of uncapped QDs (surface QDs) reveals the formation of highly uniform and dense single QDs family with increasing the annealing temperature to 850 °C, which shows the good agreement with the low temperature PL result. The impact of postgrowth RTP on the InAs/GaAs(Sb) QDs heterostructures on semi-insulating epi-ready GaAs substrates has been studied extensively, and analysis of the optical properties, morphological evolution, and crystallographic change of the QDs as a function of annealing temperature show good agreement, which gives an insight for development of futuristics solar cells devices.