Theoretical investigation of inter-surface diffusion on non-planar GaAs surfaces

We investigate the Ga adatom inter-surface diffusion between GaAs 001.- 2=4. top and GaAs 111.B- 2=2. side surfaces theoretically, based on microscopic calculations and a statistical mechanical discussion. The calculated migration potential based on the microscopic calculations imply that Ga adatoms are predominantly adsorbed on 001.surfaces. The results indicate that Ga adatoms basically diffuse from the 111.B side surface to the 001.top surface, so long as both top and side surfaces are single-domain structures. However, around the critical As pressure of surface transition, where 2=2. and ʹ19 =ʹ19.structures coexist on the 111.B side surface, boundaries exist that are covered with neither 2=2. nor ʹ19 =ʹ19.units. Since these non-covered boundaries can contain very reactive Ga adsorption sites, Ga adatoms tend to diffuse from the 001.top to the 111.B side surface, so long as non-covered boundaries appear on the 111.B side surfaces. Our theoretical investigation implies that the direction of the inter-surface diffusion between the GaAs 001.top and the 111.B side surfaces is reversed twice with increasing As pressure, which is in good agreement with the recent experimental reports. q1998 Elsevier Science B.V. All rights reserved.