Crystallographic Defects in (001) GaAs Epitaxial Layers Grown by MOCVD

The effects of all possible system parameters on the formation of crystallographic defects in (001) GaAs epitaxial layers grown by MOCVD were studied, using a wet selective photoetching technique in combination with optical microscopy, SEM, and TEM in evaluations of over 500 samples. Low arsine/TMG ratios during growth led to the formation of the so-called oval defects. Growth temperatures below 600 C were found to cause so-called boat defects, which generally contained a deformed region with dislocations, stacking faults, and, sometimes, polycrystalline material; the formation of boat defects is related to impurity adsorption at the growth surface. On exactly oriented (001) crystals, occasionally rounded plateaus were found after epitaxial growth. For growth rates lower than 3 micron/h, these were round, but for growth rates higher than 8 micron/h the plateaus were elongated in the 110-line direction. These hillocks were found to contain numerous dislocations, generated at or near the original substrate surface.