Epitaxial relationships between GaN and Al↓(2)O↓(3)(0001)substrates

摘要

GaN thin layers (200 Anstrom)were, grown by gas-source molecular beam epitaxy on c-plane Al↓(2)O↓(3) substrates. Transmission electron microscopy reveals that two different epitaxial, relationships may occur. Thc well-known GaN orientation with the c axis perpendicular to the Al↓(2)O↓(3) surface and 1100GaN‖［1120］AI↓(2)O↓(3)is observed when the Substrate is nitridated prior to the growth. On the other hand, GaN layers deposited on bsre Al↓(2) O↓(3) surfaces exhibit a different crystallographic orientation:1120)↓(GaN)‖ 1100↓(AI↓(2)O↓(3)) and 1103)↓(GaN)‖［1120］↓(Al↓(2)O↓(3)). This corrsponds to a tilt of about 19 °of the c axis with respect to the substrate surface. # 1997American Institute of Physics. S0003-6951(97)02105-0