Nitride image intensifiers

Abstract

Nitride based photocathodes for image intensifiers are of interest because of the wide span of wavelengths covered by the bandgap of the AlGaInN alloy system. The potential bandgap range for this alloy system is from 6.2 eV for AlN to 0.7 eV for InN. Coupled with microchannel plate technology, this alloy system potentially offers low noise and high gain image intensifiers over a wide wavelength range. Results from L-3 EOS work in this area are presented beginning with a brief summary of unpublished early work carried out from 1992 - 1997 on AlGaN image intensifiers. The early work wrestled with the dual issues of sealing image intensifiers along with improving the quality of the AlGaN epitaxy layer. This is followed by our current results on a GaN image intensifier sealed with a photocathode from SVTA. Imagery using 375nm LED illumination is shown. The quantum efficiency at 300nm was estimated to be 16% measured in transmission mode. This QE was achieved with a 0.15μm thick Mg doped GaN active layer.