Detailed study of HVPE-GaN doped with silicon

Abstract

The purpose of this work was to optimize the silicon doping process in gallium nitride grown using the halide vapor phase epitaxy method. Five crystal growth experiments were carried out to investigate the influence of reagent flow on the incorporation of the donor dopant. Additionally, the study examined the role of growth morphology, which was found to significantly affect the uniformity of silicon incorporation and free carrier distribution in the crystals. Crystals in this work were grown on native ammonothermal substrates of high structural quality. Silicon was the only intentional donor dopant introduced into the growth zone in the form of gaseous precursor, dichlorosilane. The structural quality, concentrations of incorporated dopants and free carriers, were analyzed for each grown crystal. The results indicated that silicon was the only electrically active, statistically relevant dopant in all of the samples. The rate of hydrogen chloride flow in the dichlorosilane line was correlated with the final concentration of silicon in the samples. The silicon and free carrier concentrations of up to 10¹⁹ cm⁻³ were noted. Silicon incorporation appeared to be non-uniform regardless of the growth conditions. Each sample exhibited a gradient of silicon and free carrier concentrations along the growth direction. It was shown that the cause of silicon gradient in gallium nitride crystals was associated with the silicon deposition inside the reactor, in the dichlorosilane line, as well as with the crystal’s growth morphology.