Confirmation of the temperature-dependent photovoltaic effect on Fermi-level measurements by photoemission spectroscopy

Soft-x-ray photoemission spectroscopy (SXPS) measurements of Fermi-level positions within the band gap of clean, GaAs(100) surfaces demonstrate that photovoltaic charging produces a major shift in the apparent band bending at low (50 100 K) temperatures. These measurements confirm recent predictions of Hecht [M. H. Hecht, Phys. Rev. B 41, 7918 (1990)], based on restoring currents limited by carrier transport through the depletion region, highlight the effects of photovoltaic charging for clean (versus metallized) semiconductor surfaces, and justify Hecht's claims for a reassessment of many previous low-temperature photoemission studies of Fermi-level movement. © 1990 The American Physical Society.