Improving the Material Quality of GaAs Grown on the c-Plane Sapphire by Molecular Beam Epitaxy to Achieve Room-Temperature Photoluminescence

High-quality GaAs on the c-plane sapphire has been achieved by employing a two-step growth technique, multiple annealing, and an AlAs nucleation layer using molecular beam epitaxy (MBE). The effect of growth parameters, namely, growth temperature, As₂ flux, and low-temperature layer growth temperature (LTLGT) in two-step growth have been investigated. In all of the grown samples, the epitaxial orientation of the film is GaAs (111)A. Unlike the homoepitaxial GaAs (111)A MBE growth, where increasing the As₂ flux improves the film quality, here the lowest As₂ flux resulted in the best film quality. Very low LTLGT resulted in highly twinned material and film surface with many pits. Growth temperature also plays an important role, as seen by the exceptional structural and optical properties of samples grown at 650 °C, but at the cost of the rough film surface. We have observed low-temperature photoluminescence (PL) for all of the samples. However, for the first time, to the best of our knowledge, room-temperature PL (RT-PL) has been demonstrated from a heteroepitaxial GaAs (111)A film. This result is important because RT-PL from the epitaxial GaAs/c-plane sapphire will lead to the fabrication of GaAs laser on sapphire, which is an important functionality to realize photonic circuits on the sapphire platform.