MINORITY-CARRIERS CONTRIBUTION AND HOT-ELECTRON INJECTION PROCESS IN TUNNEL SPECTROSCOPY OF H-PASSIVATED SILICON SURFACES

Detailed studies of the current-voltage characteristics of the STM tun nel junction with H-passivated Si(111) surfaces have been performed as a function of type and level of doping, temperature and light illumin ation of the surface. For slightly doped p-Si crystals we have observe d a main contribution of minority carriers in the reverse tunnel curre nt. For n-Si surfaces an abrupt increase of the reverse current at som e bias voltage has been found. This effect is explained by a hole accu mulation near the surface which changes band bending and initiates the hot-electron injection from the STM tip with the energy sufficient fo r the impact ionization of the carriers in the silicon. The hole accum ulation also causes a vast hysteresis of the tunnel current. It create s a new look at the point tunnel contact as a low-dimensional bistable element.