Fermi-level effect on Ga self-diffusion studied using ~(69)GaAs/~(69)Ga~(71)GaAs isotope superlattice

摘要

We have studied the Ga self-diffusion in GaAs and its dependence on Si doping using ~(69)GaAs/~(69)Ga~(71)GaAs isotope superlattices with [Si] chemical bounds 1x10~(17)-3x10~(18) cm~(-3) grown by molecular-beam epitaxy. The depth profiles of ~(71)Ga atoms before and after thermal anneals at 900 deg C have been investigated via secondary-ion mass spectrometry (SIMS) to botain the Ga self-diffusion coefficient as a function of the Si concentration. We find that the Fermi-level effect becomes dominant only in the high-doped regime, i.e., [Si]>=1x10~(18)cm~(-3), where the Ga self-diffusion coefficient increased in proportion to the third power of the electron concentration. On the other hand, no change in the diffusion coefficient was observed in the low-doped regime. Our results show that the Ga self-diffusion is driven by the Fermi-level effect and mediated by triply charged Ga vacacies in the high-doped regime, while it is suggested that some other Fermi-level independent mechanisms are operating in the intrinsic and low dooped regime.