Diffusion of Te or Zn into GaAs from Doped SiO2 Films by Rapid Thermal Processing

The n+ layers on semi-insulating liquid encapsulated Czochralski GaAs and p+ layers on Si-doped n-type GaAs were formed by rapid thermal diffusion (RTD) from Te- and Zn-doped oxide films, respectively. The Zn diffusion coefficient of the RTD sample at 850°C for 6s with the heating rate of 50°C/s is about two orders of magnitude higher than that of a similar furnacediffused sample at the same temperature. In addition, Zn and Te diffusion are strongly enhanced by the high heating rate of RTD. The shallow and abrupt p+n junction in GaAs is formed by RTD of Zn with the low heating rate. This shallow p+n junction is suitable for the construction of a photodiode. It is observed that the short wavelength spectral response (<800 nm) of the photodiode fabricated by RTD from Zn-doped oxide film decreases as the heating rate of RTD increases. Deep levels in these photodiodes were characterized by deep level transient spectroscopy. A electron trap EZ (Ec -0.57eV) is produced by RTD of Zn in the n-type substrate under p+n junction. The concentration of this trap is independent of the heating rate of RTD.