Deep levels reduction in (NH4)2S treated and annealed GaAs epilayer on Si substrate

The surface properties of GaAs/Si after ex-situ treatment with (NH4)2S solution were investigated by photoluminescence (PL) and X-ray photoelectron spectroscopy. The As 3d and Ga 3d core level studies show that the surface is free of native oxides. A 4.5-fold increase in the PL intensity was observed on undoped GaAs/Si surface after sulfur passivation. This treatment improves the electronic properties of the surface as seen from the increase in PL intensity. After the treatment, the films were annealed at 350 and 450°C in nitrogen atmosphere. Then the films are studied with deep level transient spectroscopy measurements employing metal–insulator–semiconductor structures. Two deep levels at 0.44 and 0.73 eV below the conduction-band edge are found in the as-grown, S passivated and annealed samples. In (NH4)2S treated and 450°C annealed sample the trap concentration has reduced nearly half order of magnitude.