Threading dislocation reduction mechanisms in low-temperature-grown GaAs

In these studies, we have investigated the role of low-temperature growth i n the reduction of threading dislocation (TD) densities in large mismatch h eteroepitaxy. Low- and high-temperature (LT) and (HT) GaAs growths on highl y mismatched substrates were used to find the mechanism of enhanced TD redu ction in LT grown (250 degrees C) GaAs. LT templates have symmetric (equal) TD subdensities on the {111}A and {111}B planes, whereas HT templates have asymmetric TD subdensities. A model based on TD reactions was applied to t he experimental results and confirmed the beneficial role of symmetric TD s ubdensities in LT GaAs TD reduction. A ductile-to-brittle transition in dis location behavior was observed at similar to 400 degrees C. (C) 1999 Americ an Institute of Physics. [S0021-8979(99)02821-2].