VACANCY-MEDIATED DISORDERING OF ALGAAS-GAAS SUPERLATTICES BY GROUP-IV OR GROUP-VI IMPURITY IN-DIFFUSION

We report on a study of disordering by the in-diffusion of a variety of group IV and VI n-type impurities. In all cases, the n-type dopants enhance the Al-Ga interdiffusion coefficient over that due to the As overpressure alone. The Si-induced enhancement has been previously attributed to the change in the Fermi-level position with doping and therefore, should account for disordering using other n-type impurities. However, we observe important differences in the interdiffusion characteristics induced by Si or Ge, and that by S or Se. The disordering is attributed to the enhancement in the group III-vacancy concentration for each of these n-type impurities, as is also the case in undoped crystals disordered by an As ambient alone at 855-degrees-C.