Theoretical study of GaN molecular beam epitaxy growth using ammonia: A rate equation approach

III-V nitrides are intensely researched fur optoelectronic applications spa nning the entire visible spectrum. Tn spite of realization of commercial de vices and advances in processing of materials and devices, the understandin g of the processing and epitaxial growth of these materials is incomplete. In this study, a rate equation approach is proposed based on physically sou nd surface processes to investigate the molecular bean epitaxy growth of Ga N using ammonia. A surface riding layer of Ga and ammonia and its associate d dynamics such as incorporation of Ga and N in to the crystal and desorpti on are included in the model. Rates of all surface processes are assumed Ar rhenius type. The simulated Ga incorporation rate as a function of ammonia pressure and substrate temperature are in excellent agreement with the expe rimental data. Ga incorporation increases with increasing NH3 overpressure and saturates at a maximum value at large NH3 overpressure. The Ga incorpor ation rate exhibits a peak at 820 degrees C due to competition between ther mally activated pyrolysis of NH3 and reevaporation of Ca from the surface. The simulated Ga desorption parameter versus time data is also in good agre ement with the experimental data. These observations will be explained base d on the inter-play of competing surface processes such as evaporation and incorporation. (C) 2000 American Vacuum Society. [S0734-211X(00)02903-6].