Synthesis of GaN bulk crystals and melt growth of GaN layers under nitrogen plasma

Gallium nitrides of wurtzite structure were synthesized by reacting gallium metal with atomic nitrogen in a microwave plasma operating at 200-400 Pa with the power of 420 W and the frequency of 2.45 GHz to avoid high equilibrium pressure. Polycrystalline GaN can be synthesized at low equilibrium pressures of 200-400 Pa and low temperature of 610-700 degrees C. The yield of polycrystalline GaN was increased by increasing the nitrogen plasma exposure time and reached 96% at 3 h. The growth of GaN layers on (0001) sapphire substrate was carried out using the same technique. When the sapphire substrate was placed in the bottom of the BN crucible, GaN layer of about 3 pm was grown on the substrate with the growth rate of 0.5 mu m/h. The layer was nearly oriented to (0001)GaN (0001) sapphire. These results indicate that the direct conversion of gallium metal into GaN layer under nitrogen plasma is a useful method. (c) 2007 Elsevier B.V. All rights reserved.