Supersonic Nozzle Beam Source of Active Nitrogen for Improved Nitride Growth

摘要

Hydrazoic acid was shown to be an extremely reactive molecule and an effectiveprecursor species for 'active nitrogen'. At room temperature, hydrazoic acid dissociatively chemisorbed on GaAs(110) surfaces to form the NH radical and N2. At 673 K, an anionic exchange mechanism commenced; the surface became completely depleted in As and a thin film of GaN formed. When the surface was dosed at 773 K, a 20 A thick GaN film was grown. This evidence demonstrates that hydrazoic acid is highly reactive at comparatively low surface temperatures and offers a viable alternative to ammonia as a nitrogen precursor. Experiments which involved growing GaN on sapphire and silicon using a supersonic beam of ammonia and an effusive triethylgallium beam, showed distinct trends in film morphology as a function of the ammonia nozzle and substrate temperature. Stoichiometric GaN films were deposited on Al2O3(0001), Si(001) and Si(111) substrates. Very uniform films were achieved at low substrate temperatures. An improvement in the degree of preferred orientation in the GaN films deposited on Al2O3(0001) substrates with increasing nozzle temperature was observed.