Deep levels and band bending at GaP(100) and (110) surfaces

We have observed optical transitions involving multiple, deep levels at GaP surfaces and interfaces whose energies and intensities depend on reconstruction and atomic composition. Comparison of clean GaP(100) epilayers prepared by ultrahigh vacuum decapping of protective overlayers with GaP(110) surfaces prepared by cleavage of bulk-grown crystals reveals a variation of deep level features with crystal growth as well. Comparison of these spectral distributions with Au and Al Schottky barriers measured at these surfaces by photoelectron spectroscopy and internal photoemission indicates a dominant influence of these deep levels on the Fermi level stabilization. © 1994.