Morphology and defect study in low pressure MOCVD grown AlGaAs

Abstract

A low pressure MOCVD system has been adopted to grow AlGaAs epitaxial layer on Si-doped or S.I. GaAs substrate by using TMA, TEG and AsH 3 as the sources. The effect of temperature on the surface morphology has been studied and a defect free surface has nearly been obtained. From EPMA analysis, at lower growth temperature (<710°C), the “whiskers” which were observed in this study are composed of a region with much less aluminum content than the surrounding normal region, but gallium and arsenic contents are nearly the same. There are few “precipitate hillock” defects on the epilayers especially under low growth temperature (<720°C), in which region, the aluminum content is greater than the surrounding region but gallium and arsenic contents are less. Raising the growth temperature (>750°C), both of “whisker defect” and “precipitate hillock” are eliminated. Very few “twin faults” defects and “bird-fault” defects on the epitaxial layers grown under high growth temperature were observed.