Growth model for GaN with comparison to structural, optical, and electrical properties

A kinetic model is presented to explain the metal organic vapor phase epitaxy (MOVPE) growth of GaN. The model is based upon measured desorption rates and assumptions on the precursor dissociation and sticking probabilities. The model shows how the growth temperature and V/III ratio are linked for the growth of high quality GaN films. From a comparison of growth conditions cited in the literature to the quality of GaN produced, optimal film growth appears to occur when the V/III ratio is chosen to be slightly larger than the N to Ga desorption ratio. The relationship between the growth temperature, V/III ratio, and GaN quality are explained in terms of how the growth parameters influence the incorporation of Ga and N atoms into the growing film. The Ga and N diffusion lengths are estimated to be 2-20 nm and <1 nm at 1050 degrees C, respectively, for practical MOVPE growth rates. Growth conditions for smooth (0001) surface morphology are described in terms of the growth model, as well as possible origins for defect incorporation in GaN. As a result of the large N desorption rate, it is suggested that during growth N is incorporated into the GaN lattice via an adsorption/desorption cycle. Application of the growth model to establishing the growth process conditions and run-to-run reproducibility are also discussed. [S0021-8979(98)01616-8].