Relaxation of band bending on GaAs(001) surface by controlling the crystal defects near the surface

The influence of crystal defects near the surface on horizontal Bridgman-grown GaAs(OO1) surface is investigated by photoluminescence (PL) and synchrotron radiation photoelectron spectroscopy (SRPES). PL measurements reveal that after heating to 500°C a layer with lower defect concentration exists just under the thermal degraded one. SRPES shows that the surface Fermi level (EFs) moves to the conduction band minimum when this thermally degraded layer is removed by chemically etching and the etched surface is heated in ultra-high vacuum after rinsing with the deoxygenated and deionized water. These results suggest that the position of E, for GaAs(OO1) surface is strongly affected by crystal defects near the surface