Fabrication and hard X-ray photoemission analysis of photocathodes with sharp solar-blind sensitivity using AlGaN films grown on Si substrates

摘要

Photocathode devices operating in reflection-mode, where the photoemission is detected on the same side as the light irradiation, were developed for the detection of deep ultraviolet light by using p-Al_xGa_(1-x)N films grown on Si(111) substrates. The external quantum efficiencies were as high as 20-15% at 200 nm and 280 ran, while the value was as low as 10~(-2)% at 310 nm. The on-off ratio was more than four orders of magnitude, which represents high solar-blind sensitivity. The escape probability of Al_xGa_(1-x)N photocathode was decreased with increase of A1N mole fraction. The effective barrier potential against the photoelectron emission near the surface was reduced due to the upward shift of conduction band of Al_xGa_(1-x)N The photoemission from the Al_xGa_(1-x)N films terminated with Cs-O adatoms will be discussed in terms of band diagrams that were evaluated by hard X-ray photoelectron spectroscopy.