GaN quality evolution according to carrier gas for the nucleation layer and buffer layer

The effect of the carrier gas type on the crystal quality of GaN is investigated in detail. Compared with a single carrier gas (H2 or N2), the employment of N2 during the nucleation layer and H2 in the high temperature buffer layer growth process will lead to smoother surface, stronger photoluminescence spectral strength, and lower threading dislocation density. Furthermore, it is found that conical and snowflake-like protrusions appear on the surface for the sample under pure N2 atmosphere.