Threading dislocation reduction mechanisms in low-temperature-grown GaAs

In these studies, we have investigated the role of low-temperature growth in the reduction of threading dislocation (TD) densities in large mismatch heteroepitaxy. Low- and high-temperature (LT) and (HT) GaAs growths on highly mismatched substrates were used to find the mechanism of enhanced TD reduction 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 the experimental results and confirmed the beneficial role of symmetric TD subdensities in LT GaAs TD reduction. A ductile-to-brittle transition in dislocation behavior was observed at similar to 400 degrees C. (C) 1999 American Institute of Physics. [S0021-8979(99)02821-2].