Variation of GaAs surface charge under an electron beam: effect on cathodoluminescence signal

Abstract

AbstractThis work is a self‐consistent calculation model of the GaAs surface charge under electronic bombardment. The surface charge due to surface defects can be influenced by the electron–hole pair generated at the surface zone (in the depletion region). Numerical results show that the donor states charge decreases under the cathodic excitation, but when the surface states are of acceptor type, the surface charge increases with increasing excitation levels (increasing of beam current). In the case of donor states, the cathodoluminescence (CL) intensity increases when the energy level Et, associated with the surface density Nt, is near the conduction band Ec. In the case of acceptor states, the same behavior of CL intensity has been observed when Et is near the valance band Ev. In all cases, the CL intensity decreases when Et moves to the middle of the band gap. According to this calculation, it is clear that the variation of surface charge must be taken into account in all surface analysis techniques based on electron beams. Copyright © 2007 John Wiley & Sons, Ltd.