Field-assisted photoemission to 2.1 microns from a Ag/p-In0.77Ga0.23As photocathode

Reflection-mode photoemission to a 2.1-μm threshold has been achieved from an externally biased Ag/p-In0.77Ga0.23As cathode. Quantum yield at 1.9 μm is 2×10−3 electrons per incident photon for 2.4-V bias and a cathode cooled to ∼125 K. The cathode was grown by vapor-phase epitaxy on a compositionally graded InAsP on InP (100) substrate using the hydride process.