N-polar GaN evolution on nominally on-axis c-plane sapphire by MOCVD-I: Growth

The present work is part-I of a study that demonstrates the influence of metalorganic chemical vapor deposition process parameters on the evolution of gallium nitride (GaN) deposited in a two-step growth process on c-plane sapphire substrates with a particular emphasis on nitrogen-polar GaN (N-polar GaN). First, the temperature domains of sapphire nitridation that result in Ga-polar and N-polar GaN epilayers were identified. Then, the structural and morphological evolution of low-temperature GaN nucleation layers were examined at the observed temperature domains of nitridation. Subsequently, a series of experiments were performed to study the influence of Ga and N precursor flow rates and epilayer growth temperature on the surface evolution of N-polar GaN. The observed results were analyzed in terms of thermodynamic and kinetic parameters of GaN growth. This work reports high-surface quality N-polar GaN epilayers without surface hillocks, exhibiting surface roughness about 1.5 nm over 2 x 2 mu m2 area and with good crystalline quality on nominally on-axis c-plane sapphire substrates at low epilayer growth temperatures.

Automated summary

This study demonstrates the influence of metalorganic chemical vapor deposition process parameters on the evolution of gallium nitride (GaN) and focuses on nitrogen-polar GaN (N-polar GaN). The research shows that N-polar GaN epilayers formed at low epilayer growth temperatures have high surface quality and good crystalline quality.