THE ROLE OF N-2 AND H-2 AS CARRIER GAS ON THE SELECTIVE-AREA MOVPE OFINP-BASED HETEROSTRUCTURES USING TBAS AND TBP AS GROUP-V SOURCES

Hydrogen and nitrogen have been employed as carrier gases for the sele ctive growth of InP-based materials on patterned substrates using tert iarybutyl-arsine (TBAs) and -phosphine (TBP) as alternative group-V so urces at different reactor pressures. The properties of the deposited layers have been found to be mainly determined by the diffusion coeffi cient in the vapour phase, which increases by reducing the reactor pre ssure or using H-2 instead of N-2. A higher edge growth, combined with a smaller zone of enhanced growth and, where appropriate, In-enrichme nt near the masks was detected at atmospheric pressure deposition and for the use of N-2, respectively. Furthermore a higher selectivity has been observed for both carriers at reduced reactor pressures and when using H-2 instead of N-2. Nitrogen as carrier gas offers an additiona l independent parameter to control the properties of selectively depos ited layers and reduces the safety risks of the MOVPE process especial ly when being combined with less toxic group-V sources. (C) 1997 Publi shed by Elsevier Science S.A.