Photoluminescence and deep-level transient spectroscopy of DX-centers in selectively silicon-doped GaAs-AlAs superlattices

Abstract

Deep level transient spectroscopy (DLTS) and photoluminescence (PL) measurements are used to characterize short period selectively or uniformly Si-doped GaAs-AlAs superlattices (SLs) grown by molecular beam epitaxy at two different temperatures. DLTS measurements show the presence of DX center with an apparent activation energy of 0. 42eV and a trap concentration which decreases as the growth temperature is lowered. From an analysis of the DX concentration and binding energy we show that this center is mainly located in the AlAs layers. The high growth temperature enhances the silicon diffusion from the GaAs wells towards the AlAs layers which allows us to detect the DX even when only the GaAs layers are doped. The PL measurements performed on the near band edge show different transitions. No deep luminescence in the near infra-red spectrum is observed on these MBE layers despite the high DX concentration.