Growth kinetics of GaN and effects of flux ratio on the properties of GaN films grown by plasma-assisted molecular beam epitaxy

Abstract

The kinetic processes of GaN growth using plasma-assisted molecular beam epitaxy (PAMBE) have been investigated employing a precursor-mediated model. Using the highly efficient radio-frequency (rf) plasma source which produces sufficient atomic nitrogen with a low density of ions having low kinetic energy, significant ion-induced desorption is not observed, and the growth kinetics are determined by the flux ratio between Ga and N, JGa/JN. It is found that the growth rates obtained by the precursor-mediated model fit well with the experimental results, implying that the growth kinetics are effective in describing the film growth by PAMBE. Also, it is found that the flux ratio JGa/JN is one of the most important factors which determine the growth mode, degree of crystallinity, and electrical and optical properties of GaN films. Although the growth rate is high (∼680 nm/h), the surface morphology and crystalline quality of the films grown at a higher Ga flux are found to be significantly improved due to the two-dimensional layer-by-layer growth mode [root-mean-square (rms) roughness ≈1 nm]. Their electrical and optical properties are also discussed.