LUMINESCENCE FROM GOLD-PASSIVATED GALLIUM-ARSENIDE SURFACES EXCITED WITH A SCANNING TUNNELING MICROSCOPE

A scanning tunneling microscope (STM) is used to investigate light emission induced by electron tunneling into GaAs. Reproducible results are obtained iii air on cleaved (110) surfaces passivated with a thin (approximately 1.6 nm) gold film. The luminescence spectrum is dominated by recombination of thermalized electron-hole pairs. In p-type material, the light emission threshold is at, 1.45 V bias voltage. close to the band gap at 300 K. The quantum efficiency of this minority-carrier injection process increases quadratically with increasing bias voltage. In n-type material, the current induced edge emission occurs at a much higher threshold of U > 3.2 V, giving evidence for the onset of hole production via im act ionization by the injected hot, electrons.