Al-Ga Interdiffusion, Carbon Acceptor Diffusion, and Hole Reduction in Carbon-Doped Al(0.4)Ga(0.6)As/GaAs Superlattices: The As(4) Pressure Effect

摘要

Al-Ga interdiffusion, carbon acceptor diffusion, and hole reduction were studiedin carbon doped Al(0.4)Ga(0.6)As/GaAs superlattices (SL) annealed under different ambient As4 pressure conditions in the temperature range of 825-960 deg C. The SL were doped with carbon to an initial acceptor concentration of approx. 2.9 x 10(exp 19)/cu cm. Al-Ga interdiffusion was found to be most prominent under Ga-rich annealing ambient conditions, with interdiffusivity values, D sub(Al-Ga), turned out to be about two orders of magnitude smaller than those predicted by the Fermi-level effect model. Under As-rich ambient conditions, the D sub(Al-Ga) values are in approximate agreement with those predicted by the Fermi-level effect model. The hole concentrations in the SL decreased significantly after annealing under As-rich and As-poor ambient conditions, while those after annealing in the Ga-rich ambient were almost totally intact. By analyzing the measured hole concentration profiles, it has been found that both carbon acceptor diffusion and reduction have occurred during annealing. Both the carbon acceptor diffusivity data and the carbon acceptor reduction coefficient data are characterized approximately by a dependence on As4 pressure values to the one quarter power. These As4 pressure dependencies indicate that carbon diffuses via the interstitialcy or interstitial-substitutional mechanism while hole reduction is governed by a carbon acceptor precipitation mechanism.