Photovoltage effects in photoemission from thin GaAs layers

A set of thin GaAs p-type negative electron affinity (NEA) photocathodes have been used to measure the yield of photoemitted electrons at high intensity excitation. The active layer thickness is 100 nm and the p-type doping ranges from 5×1018 to 5×1019 cm−3 for a set of four samples. The results show that the surface escape probability is a linear function of the NEA energy. The surface photovoltage effect on photoemission is found to diminish to zero at a doping level of 5× 1019 cm−3. The experimental results are shown to be in good agreement with calculations using a charge limit model based on surface photovoltage kinetics that assume a constant electron energy relaxation rate in the band bending region.  2001 Elsevier Science B.V. All rights reserved. PACS: 29.25.Bx; 73.50.Pz; 73.61.Ey; 79.60.-i; 85.60.H