Effect of As molecular species on inter-surface diffusion in GaAs MBE for ridge structure fabrication

The faceting and the shrinkage processes of ridge structure fabricated alon g [1 1 0] on GaAs (0 0 1) substrate with As-2 flux and As-4 flux were monit ored by microprobe reflection high-energy electron diffraction/scanning ele ctron microscopy (microprobe-RHEED/SEM) installed in the MBE chamber. It wa s found that the shrinkage of top size with As-4 flux was faster than that with As-2 flux. To analyze the result of the experiments, the calculation b ased on two-face inter-surface diffusion model was conducted. From this cal culation, we show that the shrinkage of the top size is slower when the ars enic pressure is higher, simply because the lateral flow of Ga adatoms towa rds the top surface becomes smaller. Under the As-2 flux, the amount of Ga adatoms which migrate to (0 0 1) surfaces from (1 1 1)B surface becomes sma ller compared with that under As-4 flux due to the higher reactivity of As- 2 to Ga adatoms. (C) 2001 Elsevier Science B.V. All rights reserved.