KINETIC-STUDY OF THE EFFECTS OF H, O, N, S, NO, NO2 AND O-2 ON THE SURFACE-STATES OF INGAAS AND GAAS

The photoluminescence intensities (PLIs) from 300 nm layers of In0.53Ga0.47As and GaAs have been used to monitor carrier lifetimes, in situ, during exposure of their surfaces to a number of gaseous species at 25 degrees C. PLIs have been observed to increase by a factor of 30-50 following a few seconds exposure to atomic hydrogen at gas-phase atom densities of ca. 10(13) cm(-3). For both semiconductors the PLI was found to be ca. 40% lower while the surface was being exposed to these atoms. Additional exposure of the InGaAs to H atoms was found to reduce the PLI from this maximum by a factor of 2-3. Both the InGaAs and GaAs surfaces that had been passivated by hydrogen atoms could be de-passivated in less than a second by exposure to O, N, NO or NO2 at comparable gas-phase densities or, at a much slower rate, by exposure to O-2. The surfaces thus formed could be re-passivated by exposure to atomic hydrogen, but in the case of oxidizing species, the original behaviour of the InGaAs surface could only be restored with an HF wash. X-Ray photoelectron (XP) spectra of the surfaces under all these conditions were found to be indistinguishable. Exposure of the surface to S atoms was found to improve the passivation level of an HCl-washed surface by almost four orders of magnitude.