Quantitative study of thermal diffusion of elements across a ZnSe/GaAs interface using SIMS

ZnSe epilayers were grown on GaAs substrates, which had been treated with S e and Zn prior to the growth process. Thermal diffusion of elements across the interface was investigated, using secondary ion mass spectroscopy (SIMS ). Ion-implanted standards have been used to calculate the "useful ion yiel d" for Zn and Se in the GaAs matrix and for Ga and As in the ZnSe matrix. C onsequently, SIMS raw data were converted to quantified data. Diffusion of Ga atoms across the interface was observed for Zn-pretreated substrates. A comparison study showed that Se pretreatment of the GaAs substrate prevents thermal diffusion of Ga across the interface. This effect is believed to b e due to the formation of GaAs,Se, layers at the interface, which acts as a barrier to diffusion. The Ga diffusion coefficients at annealing temperatu res of 400 degrees C, 500 degrees C and 600 degrees C were found to be 2.1 x 10(-16) cm(2)/s, 1.9 x 10(-15) cm(2)/s and 2.2 x 10(-14) cm(-2)/s, respec tively. The thermal diffusion of other elements across the interface was no t observed within the resolution limit of SIMS analysis.