The chemistry of sapphire nitridation in relation to the GaN structural quality: Why low temperature 200°C nitridation?

The effect of c-plane sapphire nitridation upon exposure to an rf N2 plasma at temperatures in the range 100-700°C on the quality of GaN epilayers grown by MBE is investigated. A homogeneous AlN layer is formed at 200°C. Nitridation at higher temperatures creates a rough and non-homogeneous nitridated layer including both AlN and NO. Lowering the nitridation temperature to 200°C results in the improvement of the GaN structural and photoluminescence properties. The results are interpreted in the framework of a chemical model based on the competition between formation of AlN and NO whose adsorption/desorption equilibrium on the sapphire surface strongly depends on temperature

Duke Scholars

Author April S. Brown Electrical and Computer Engineering