Scattering of NH from reconstructed GaAs 100/surfaces

Scatterings of pulsed NH3 beams from c 4=4.-, 2=4.-, 1=6.-reconstructed GaAs 100.surfaces are examined. The reconstruction-controlled surfaces are prepared by molecular beam epitaxy MBE.and subsequent treatments. It is found that the observed time-of-flight time-of-arrival.spectra have a long tail corresponding to a long surface residence time at a trapping potential of the surface. The depths of the trapping potential are estimated from the temperature dependence of the surface residence time to be 0.526"0.031, 0.632"0.017, and 0.513"0.024 eV for the c 4=4., 2=4., and 1=6. surfaces, respectively. The depth of the trapping potential is explained by the electrostatic interaction generated by the charge distribution of the reconstructed GaAs surfaces. The observed results indicate that the surface reaction related to nitride growth is described within the framework of the precursor-mediated mechanism. q1998 Elsevier Science B.V. All rights reserved