Field-assisted minority carrier electron transport across a <i>p</i>-InGaAs/<i>p</i>-InP heterojunction

Abstract

A field-assisted photocathode has been made which has a reflection yield quantum efficiency of ∠1% out to a wavelength of 1.6 μ. The cathode is a heterojuncation InP/InGaAs/InP structure fabricated by a hybrid VPE/LPE process. Photoelectrons generated for wavelengths ?1 μm must cross a p-InP/p-InGaAs heterojunction, under bias. To achieve high transfer across the p–p heterojunction, the heterojunction must be carefully lattice matched, the InP emitter must be ?1 μm thick and have p-type doping in the low 1015 cm−3 range, the InGaAs layer must have doping in the low 1016 cm−3 range, and the heterojunction composition grading distance must be ?1000 Å. These criteria are all met by the VPE/LPE grown heterojunction. Heterojunction transfer efficiencies approaching 100% for bias voltages 3–5 V have been measured.