Defects in III nitrides

Defects were investigated in undoped GaN and AlGaN epilayers grown on Al/sub 2/O/sub 3/ substrates by metal organic vapor phase epitaxy. Threading dislocations (TDs) and horizontal dislocations (HDs) in GaN were imaged and classified into different types. Precipitates and their punching out dislocations were recognized in undoped AlGaN. Defects at AlGaN/GaN interface are analyzed to result from compressive stress.