SHIFT OF SURFACE FERMI-LEVEL POSITION TOWARD THE CONDUCTION-BAND MINIMUM BY CRYSTAL DEFECTS NEAR GAAS(001) SURFACE

The effects of crystal defects near the surface on the position of sur face Fermi level (E-FS) are investigated using photoluminescence (PL) measurements and synchrotron radiation photoelectron spectroscopy (SRP ES). For the lightly Si-doped GaAs(001) surface, PL measurements revea l that after heating to 500 degrees C a layer with lower PL peak inten sities related to gallium vacancies than those of the bulk exists just under the thermal degraded layer. SRPES shows that E-FS moves upward to 1.1-1.17 eV above the valence band maximum when this thermal degrad ed layer is removed by chemical etching and the excess arsenic on the surface, which is formed by rinsing the etched surface with deoxygenat ed and deionized water, is evaporated by heating in ultrahigh vacuum ( UHV). After evaporation of excess arsenic on the surface by heating, t he etching-depth dependence of E-FS for a Sample preheated in UHV corr elated with the existence of this defect concentration layer. These re sults suggest that the position of E-FS for the GaAs(001) surface is s trongly influenced by crystal defects near the surface. (C) 1997 Ameri can Institute of Physics.