X-ray photoemission and photoreflectance study of Au ultrathin Si/n-GaAs Schottky contacts and hydrogen plasma treated semi-insulating GaAs surfaces

The paper presents room temperature photoreflectance measurements carried o ut on the Au/ultrathin Si/n-crystalline GaAs structure with the silicon int erlayer thickness gradually changing from about 4-27 Angstrom prepared in s itu under ultra-high-vacuum conditions. A continuous change of the phase sh ift of the corresponding photoreflectance signal of more than 180 degrees h as been observed in the Eg-critical-point oscillation of GaAs depending on the Si interlayer thickness. The explanation of the effect is based on the composition changes of the Au/Si interface monitored by X-ray photoelectron spectroscopy. The photoreflectance results are compared to the photoreflec tance signal phase changes observed on the semi-insulating GaAs surfaces ex posed to the low-temperature hydrogen plasma. (C) 1999 Elsevier Science S.A . All rights reserved.