Description

AlN epilayers were grown on (0001) sapphire substrates by metal‐organic vapor phase epitaxy (MOVPE), and the influence of substrate's surface structure on the formation of in‐plane rotation domain is studied. The surface structure of sapphire substrate is found to change during thermal cleaning and temperature ramp‐up. The oxygen‐terminated surface with monolayer (ML) steps having ABAB stacking is attributed to cause the formation of a small‐angle grain boundary (SAGB). To suppress the formation of such a special grain boundary, the two‐step temperature growth technique was employed. It was found that a proper timing of the low‐temperature buffer layer (LT BL) growth is necessary to eliminate the SAGB. Moreover, the BL growth temperature (Tg) is also found to affect the surface morphology and structural quality of AlN epilayer. The optimized LT BL Tg is found to be 1050°C. The optical emission property by cathodoluminescence (CL) measurements showed higher emission intensity from AlN epilayer without SAGB.

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