GaAs layer on c-plane sapphire for light emitting sources

Abstract

High-quality cubic GaAs (111)A buffer layers have been grown on an atomically flat c-plane trigonal sapphire substrate having well-defined steps and terraces. A two-step growth method has been used where, at an early stage, a GaAs layer has been grown at low temperature (LT), followed by second high-temperature GaAs growth layer. In addition to the two-step growth process, an AlAs nucleation layer and multiple annealing steps have been employed. The effectiveness of the LT GaAs layer in this highly dissimilar epitaxy was then investigated. An LT GaAs layer resulted in a relaxed GaAs buffer with smooth surface morphology and high crystalline quality. An InGaAs quantum well (QW) was epitaxially grown on the 70 nm GaAs buffer and compared with a reference InGaAs QW grown on a GaAs (111)A substrate. Along with x-ray and high-resolution cross-section transmission electron microscopy, comparable QW photoluminescence intensity and linewidth with respect to reference InGaAs QW confirmed the effectiveness of our growth strategies to produce high-quality GaAs on sapphire. This demonstrates the opportunity for GaAs photonics on sapphire and the potential to realise an integrated microwave photonic chip on a sapphire platform.