Effect of substrate mis-orientation on GaN thin films grown by MOCVD under different carrier gas condition

摘要

We have studied the effect of a slight mis-orientation angle on surface and crystal quality of GaN thin films grown under different carrier gas conditions. Two types of carrier gas conditions were applied to the growth. One was pure H_2 and the other was mixed N_2/H_2. As the result, we found dependence of surface and crystal quality of GaN thin films on the substrate mis-orientation angle, and they indicated almost the same tendency under both growth conditions. Therefore, it was confirmed that mis-orientation angle of sapphire substrate was one of the most critical factors for GaN thin films. Then, the effect of the additional N_2 into the conventional H_2 carrier gas was studied, and we found that the conversion of carrier gas from the conventional H_2 to N_2/H_2 mixture was effective against degradation of GaN crystallinity at any mis-orientation angle. Considering that the crystal quality of GaN thin films became insensitive to mis-orientation angle as the condition became more suitable for GaN growth, the optimal substrate mis-orientation angle was consequently decided to be approximately 0.15° from the morphological aspect.