INSITU OVERGROWTH ON GAAS PATTERNED BY FOCUSED-ION-BEAM-ASSISTED CL-2 ETCHING

In situ pattern formation of GaAs by focused-ion-beam (FIB)-assisted Cl2 etching followed by overgrowth by molecular-beam epitaxy (MBE) has been studied. In situ Auger electron spectroscopy (AES) measurements of the etched samples showed that preferential sputtering of As, which was observed on a GaAs surface processed by ion sputtering, did not take place on a GaAs surface processed by FIB-assisted Cl2 etching. The surface morphology of the overgrown AlGaAs layer on the in situ patterned substrates were excellent. Observations of the cross-sectional view in the etched region of an overgrowth sample showed that the interface between the etched surface and the overgrown layer was flat, and that no undulations caused by etching were observed. A 1-mu-m linewidth with a 2-mu-m pitch line-and-space pattern of GaAs covered with an AlGaAs layer was obtained by a combination of FIB-assisted Cl2 etching and subsequent MBE overgrowth.