Photoelectric Emission and Work Function of InP

The work function and photoemissive properties at photon energies between 2.5 and 6.2 eV have been measured for the (110) surface of InP cleaved in high vacuum and covered with various amounts of cesium. The work function of the clean surface is 4.65±0.1 eV. With the interpretation that the measured photoelectric threshold $\Phi =5.69\mathrm{}$ eV corresponds to excitation from the top of the valence band at the surface, one obtains an electron affinity $\chi =4.40\mathrm{}$ eV and a position of the Fermi level with respect to the top of the valence band ${(E_F-E_v)}_S=1.04\mathrm{}$ eV at the surface. The photoelectric yield and energy distributions from the cesium-covered surface disclose the existence of two broad peaks in the density of states in the conduction band. Structure due to critical points is observed in the yield spectrum and can be correlated with the corresponding structure in reflectivity.