Growth of single crystalline GaN from chlorine-free gas phase

This work is focused on the development of GaN bulk growth to overcome some limits of the established HVPE method. Evaporated Ga is transported by a carrier gas to the substrate where it reacts with atomic nitrogen from the ammonia decomposition to form GaN at temperatures of 1000-1200 degrees C and pressures of 200-800 hPa. To prove the methods potential, I man thick polycrystalline layers were deposited on the substrate holder with rates up to 50 mu mh(-1). Numerical simulations of temperature-, flow- and concentration field of the gas species were used to optimize crucible geometry and growth regime. It was experimentally found that in addition to temperature, total pressure and ammonia flow other parameters like source composition; crucible material and flow conditions near the substrate may affect seeding, growth rate and layer quality. First epitaxial layers up to 280 mu m thickness were successfully grown on different bulk and template substrates.