OXIDATION PROCESSES IN UNDOPED GAAS AND IN SI-DOPED GAAS

Samples of undoped GaAs- and Si-doped GaAs were oxidized at different oxidation temperatures, for different durations. Three different experimental techniques that complete each other were used: Raman scattering, Auger electron spectroscopy, and the ellipsometry technique. The growth of crystalline arsenic layer takes place after oxidation during 10 h, 45 min, and 5 min at temperatures of 400, 500, and 600-degrees-C, respectively. The oxide layer is formed as a result of three competing processes: diffusion in accordance with Fick's law, diffusion with larger diffusion coefficient through the oxide layer, and stopping of diffusion by the crystalline arsenic layer that grows at the GaAs/oxide interface. The effect of Si doping on the oxidation process of GaAs is to impede the crystallization of the arsenic layer, to diminish the diffusion coefficient in the course of the initial stages of the reaction between the oxygen and GaAs, and to cause a small rise in the activation energy.