Influence of growth temperature and post-growth annealing on optical emission from GaAsBi/AlGaAs double parabolic quantum well structures

GaAsBi/AlGaAs double parabolic quantum well (DPQW) structures were grown by solid-source molecular beam epitaxy (MBE) and investigated to evaluate the effects of growth temperature and post-growth annealing on their optical properties. Two structures, S1 and S2, were deposited using identical layer designs but with different thermal treatments. Sample S2 was subjected to an elevated substrate temperature during the growth of layers following the second GaAsBi quantum well (QW), along with an additional in situ annealing step. Temperaturedependent and excitation-dependent photoluminescence (PL) measurements revealed that the optical emission from sample S2 was significantly enhanced, with a nearly fivefold increase in room-temperature PL intensity and a blueshift of 75 meV compared to sample S1. That was attributed to reduced defect density and Bi out-diffusion during high-temperature exposure. Post-growth rapid thermal annealing (RTA) of sample S1 further confirmed the sensitivity of GaAsBi QWs to thermal treatment: annealing at 650 °C resulted in reduced PL intensity and a blueshifted emission, while annealing at 700 °C completely suppressed QW-related emission and introduced new bands attributed to defect-related transitions and Bi quantum dots (QD). These results demonstrate the crucial role of growth temperature and annealing in tailoring the emission properties of GaAsBi/AlGaAs DPQW structures for potential optoelectronic applications.