DEPENDENCE OF ARSENIC ANTISITE DEFECT CONCENTRATION AND 2-DIMENSIONALGROWTH MODE ON LT GAAS GROWTH-CONDITIONS

We investigated the dependence of Arsenic antisite defect concentratio n and that of epitaxial thickness (t(epi)), above which a transition t o three dimensional growth appears, on the growth conditions of LTGaAs layers grown by MBE. The antisite defect concentration and the lattic e expansion of LT layers grown at 180 degrees C-250 degrees C initiall y increases with increasing pressure ratio P-As4/P-Ga and then saturat es. On the other hand, t(epi) decreases with increasing P-As4/P-Ga and depends strongly on the presence of roughness on the substrate surfac e. Our results indicates that the transition to 3D growth in LT layers is caused by the reduced surface mobility of the atoms impinging on t he growth front during the epitaxy. We also determined the optimum LT growth conditions in order to achieve both maximum As-Ga concentration (similar to 1.4 x 10(20) cm(-3)) and a smooth surface without a trans ition to 3D growth. (C) 1998 Elsevier Science B.V. All rights reserved .