STUDIES OF ZINC DIFFUSION IN GALLIUM-ARSENIDE BY RAPID THERMAL-PROCESSING

Rapid thermal annealing has been used to diffuse Zn into GaAs from a thin film zinc silicate source prepared by atmospheric pressure chemical vapor deposition. For a diffusion temperature of 650-degrees-C, comparisons were made with conventional, open-tube furnace annealing and the diffusivities were found to be similar, in contrast to previous experimental work. In the temperature range 650-750-degrees-C, sharp zinc diffusion profiles are observed. Above 750-degrees-C, kinks are seen in the diffusion profiles. These kinks are also observed when semi-insulating substrates are used instead of silicon doped n+ -substrates. Previously, we have introduced a zinc diffusion model based on the pairing of interstitial Zn with all acceptor species present during diffusion. The dominant species are found to be substitutional Zn and the gallium vacancy, where the concentration of the latter is a function of the background doping concentration. The results of this model are shown to agree with all of our experimental evidence and are also consistent with our experimental observation of two distinct activation energies for zinc diffusion into n+ -doped GaAs substrates, 1.1 eV and 2.6 eV for temperatures above and below approximately 790-degrees-C, respectively.