ARSENIC MEDIATED RECONSTRUCTIONS ON CUBIC (001)GAN

The 4x1 (respectively 1x1) (001) GaN surfaces obtained when molecular- beam-epitaxy (MBE) growth is carried out on (001) cubic SiC were expos ed to an As background pressure in the MBE chamber: The reconstruction s rapidly and irreversibly changed to 2x2 [respectively c(2x2)] as usu ally observed for GaN growth on (001) GaAs. The usual reversible 2x2/c (2x2) transitions were consequently observed when bringing the Ga flux up or down. The respective positions for the 4x1/1x1 and 2x2/c(2x2) t ransitions were worked out as a function of the growth parameters. The se observations indicate that the 2x2 and c(2x2) GaN surface reconstru ctions are mediated by As atoms which we tentatively assign to a surfa ctant effect. A simple structural model involving As dimers is propose d that accounts for Ga coverages of 0.5 and 1 monolayer for the 2x2 an d c(2x2) growth regimes, respectively. (C) 1997 American Institute of Physics.