Quantum well intermixing enhanced by InP grown by He-plasma assisted GaS source MBE
Studies have been carried out on the enhancement of quantum well intermixing (QWI) using the defects present in an epitaxial layer of InP grown by He-plasma assisted gas source molecular beam epitaxy (He*–InP). The structures investigated were single and double InGaAsP quantum wells (QW) with an InGaAsP barrier. QWI was implemented using rapid thermal annealing (RTA) and measured using low-temperature photoluminescence (PL) spectroscopy. Changes in the PL emission wavelength and intensity were investigated as functions of anneal temperature and time, He*–InP layer thickness, He*–InP layer to QW distance and separation of the QWs in the two QW structure. The PL emission from the single QW structure exhibits a blueshift which increases monotonically with increasing anneal temperature and time, and decreases with the distance between the He*–InP layer and the QW. For the double QW samples, initially only the upper QW emits PL but as the anneal conditions increase in temperature and time the PL emission switches to the lower QW. The defect mechanisms responsible for the interdiffusion processes due to the defects present in the He*–InP layer are discussed, and a tentative explanation of the PL blueshift and intensity behaviour is proposed.