Effects of Surface Conditions on Carrier Transport in III-V Compounds

摘要

Surface chemical and potential measurements carried out by XPS (x-ray photo-emission spectroscopy) are reported for several GaAs materials. The GaAs samples had (100) and (110) orientations, n- and p-type doping, and both bulk and VPE grown materials were studied. Various surface treatments which included chemical etching, annealing, oxidation, gas exposure, and deposition of materials were investigated. The thermal cleaning process was shown to be associated with the surface chemical reaction As2O3 + 2GaAs yields Ga2O3 + (4/x)As(x) gas. A variation in GaAs interface Fermi-level position of up to 0.7 eV was observed. The difference in interface Fermi-level position for n- and p-type samples subjected to identical surface treatments was observed to be nearly constant at approx. = 0.3 eV. A single defect model with multiple charge states is suggested as the simplest explanation for the observed interface-potential variations. Progress toward the development of a contactless C-V apparatus is described. (Author)