Growth of gallium nitride by HVPE

The two mechanisms involved in the growth of (00.1) GaN HVPE have been dedu ced from the numerous experiments performed on (001) GaAs by the chloride m ethod. They include a desorption of adsorbed Cl as HCl by H-2 for the first mechanism and a desorption of two Cl as GaCl3 by GaCl for the second one. Theoretical curves have been computed by taking into account the interactio ns between the mass transfer, approximated by a simple model, the parasitic GaN deposition and the kinetics. They give a good approximation to the exp ected and observed growth rate values. A new domain of growth experimentall y observed in conditions of expected fast etching by HCl ensures growth rat es of 50-60 mum h(-1) without parasitic GaN deposit by using a suitable tem perature profile. This profile is computed by considering a combined mechan ism of Cl desorption by GaCl as GaCl2 and of etching by HCl. The produced G aCl2 has to be supposed to be decomposed fast with respect to the mass tran sfer velocity. Its formation rate in the vapour phase has to be supposed to be very slow with respect to the reverse reaction. These assumptions are i n agreement with the difficulty of observing this species and the well know n doubt of its existence.