Evolution of Auger peaks in GaP(110) with hydrogen chemisorption

Auger spectroscopy flanked by energy loss spectroscopy was used to investigate the evolution of GaP(110) surface electronic structure upon hydrogen exposure. The paper is focussed on the modification of PL(2,3)VV Auger line shape as a function of hydrogen exposure in the exposure range between zero and Ga3d surface exciton quenching. The discussion is concentrated on the Auger emission region about 9 eV below the emission from valence band top. The line shape change can be explained on the basis of present knowledge of electronic structure of H:GaP(110) surface and ascribed to the birth of a hydrogen-induced state (H-4) at similar to 4.4 eV below valence band top. Moreover the surface stoichiometry was monitored by Auger spectroscopy through the PL(2,3)VV to GaM(2,3)M(4,5)M(4,5) peak-to-peak ratio which was found to be extremely affected at high hydrogen exposures.