Suppression of AlGaAs/GaAs superlattice intermixing by p-type doping

We report a systematic investigation of the effect of n- and p-type doping on the AlGaAs/GaAs superlattice (SL) intermixing using photoluminescence. We find that the SL intermixing is not only enhanced by Si doping but also suppressed by Be doping. Although previous models have suggested the contribution of triply negatively charged Ga vacancies, V-Ga(3-), in n-type and intrinsic materials and of doubly positively charged Ga interstitials, I-Ga(2+), in p-type materials, we find that at 900 degrees C the Al-Ga interdiffusion is mediated by singly negatively charged Ga vacancies, V-Ga(-), in both p- and n-type materials for n < 1 x 10(18) cm(-3). These results are shown to be explained consistently in terms of the Fermi-level effect. Our results demonstrate that the thermal stability of AlGaAs/GaAs heterostructures can be controlled, i.e., weakened or strengthened, by appropriate tuning of the Fermi level.