Compositional Modulations and Vertical Two-Dimensional Arsenic-Precipitate Arrays and in Low Temperature Grown Al_0.3GA_0.7AS

Abstract

Compositional modulations and arsenic precipitates in annealed A10.3Ga0.7As layers which were grown at a low substrate temperature (200° C) by molecular beam epitaxy (MBE) were studied by transmission electron microscopy (TEM). These layers were used as surface layer which were applied on metal-insulator-semiconductor (MIS) diode. The planar and cross sectional TEM micrographs reveal that compositional modulations occurred when the thickness of LT AIGaAs was over 1500Å. The wavelength of the modulations varies between 100-200 Å and the direction of the modulation is along \011]. The arsenic precipitates were formed after annealed and the distribution of them followed the compositional modulation. Vertical two dimensional arsenic-precipitates arrays were arranged in the low aluminum constitute region. These novel microstructures result from the strain-induced spinodal decomposition and the arsenic precipitates redistribution process.