Photoelectric Emission and Interband Transitions of GaP

Abstract

The photoelectric yield spectrum and energy distributions of the emitted electrons have been measured at photon energies between 3.0 and 6.0 eV on the (110) surface of GaP. Preparation of the emitting surfaces included cleavage in ultrahigh vacuum and deposition of various amounts of cesium. The results are interpreted in terms of direct optical transitions and compared with other optical properties. Photoelectric emission furnishes evidence supporting the interpretation of reflectivity data by Bergstresser et al., and Woolley et al., and the electro-reflectance studies of Cardona and co-workers. Good agreement is found with the band structure of GaP computed by Cohen and Bergstresser.

Photoemission and band structure

“…I n measurements on crystals cleaved, for instance, in vacuum, considerable errors occur in the measurement of the energy distribution owing to the electric field a t the edges of the crystals [29]. For GaP the work function on the plane surface is p = 1.3 eV, whereas it is p = 4.5 eV for oxide-coated edges.…”