Improvement of Cutoff Characteristics for In0.11Ga0.89N-Based Photocathodes Using Light-Emitting Diode Real Time Spectral Sensitivity Monitoring System

We have fabricated photomultiplier tubes (PMTs) with photocathodes consisting of In0.11Ga0.89N films. To realize sharp cutoff characteristics of the In0.11Ga0.89N-based photocathodes, a "real time" monitoring system was employed. This system utilized light sources of light-emitting diodes (LEDs), and their peak wavelengths are 285, 375, and 470 nm respectively. With this monitoring system, PMTs with InxGa1-xN-based photocathodes are realized to demonstrate sharp cutoff characteristics over three orders of magnitude with high quantum efficiencies (QEs).