Experimental and theoretical studies on deep-level defects in n - and p -type BGaAs alloys

We report on experimental and theoretical studies of deep-level defects in BGaAs alloys, with a particular focus on the effects of rapid thermal annealing (RTA) on their electrical and optical properties. The n- and p-type BxGa1−xAs layers, with varying boron concentration ranging from 0% to 2.0% (dilute borides), were grown by molecular beam epitaxy on GaAs at a substrate temperature of 400 °C and subsequently ex-situ annealed at 700 °C. Deep level transient spectroscopy (DLTS) was employed to investigate the properties of deep-level defects and their evolution upon annealing. In addition, density functional theory (DFT) was used to calculate defect formation energies and charge transition levels, enabling the identification of native point defects and defect complexes observed in DLTS experiments. Based on the obtained DFT results, we discuss the origin of the observed trap levels, with particular emphasis on B-related defects. We also found that RTA significantly affected both the carrier concentration and the total trap concentration in n- and p-type BGaAs as the boron content increased. Furthermore, annealing impacts the emission properties and overall optical quality of these dilute borides.