Investigation of Ga diffusion in (001) and (111) CdTe layers grown on (001) GaAs

A secondary ion mass spectroscopy study of Ga diffusion in CdTe grown on (001) GaAs is reported. The layers were grown by pulsed laser evaporation and epitaxy. Two characteristic regions with increased Ga concentration were found. The first was the CdTe/GaAs interface where the concentration of Ga decreases rapidly to the detection limit of ∼ 8 x 10 14 cm -3. This region was usually less than 300 nm wide. The second was a surface region with a Ga accumulation of up to ∼ 10 17 cm -3 lon imaging revealed that in the (001) CdTe layers, Ga accumulates near the surface at localized spots, up to about 8 μ in diameter. This feature is less apparent in the (111) CdTe layers. Annealing at 500 degrees C for 1 h increased the Ga concentration in the whole layer to above 10 16 cm -3. The authors also observe thermal annealing induced precipitation of Ga at the surface of bulk CdTe samples which were originally uniformly doped with Ga