GaAs growth selectivity using a GaN mask by MOMBE

We investigated the scattering adsorption and desorption.of trimethylgallium TMG. from GaN surfaces using a pulsed-molecular beam in order to obtain information on the mechanism of growth suppression on the GaN mask during selective area growth SAG.of GaAs. The GaN mask with the highest growth suppression was formed on a GaAs 100. substrate using dimethylhydrazine DMHy.at a substrate temperature of 6408C. The time-of-arrival TOA.spectra of the TMG reflected from the surface were measured using a cryoshrouded quadrupole mass spectrometer QMS.when pulsed TMG beams were introduced to the surface. We observed that the TOA spectrum of TMG scattered from the GaN surface had a long tail, corresponding to the surface residence of TMG during scattering. It is recognized that TMG desorbs on the GaN surface without decomposition, although TMG was temporarily trapped in the precursor state. We consider that the GaAs growth suppression on a GaN surface becomes higher when the surface structure is highly stabilized. q1998 Elsevier Science B.V. All rights reserved.