Advances in wide-band gap semiconductor based photocathode devices for low light level applications

Melville P Ulmer*, Bruce W Wessels, O. H W Siegmund

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

8 Scopus citations


The basic requirement for a imaging low-light level system (one capable of single photon counting) is that the device has low dark current. Photocathode based devices have the advantage over solid state devices in this regard as the dark current is inherently low. A further requirement for UV detectors is the necessity to suppress the sensitivity in the red. and wide-band gap semi-conductors fill this role well. For nitride based semi-conductors, there is still the issue of making p-type material and making alloys with Al or In to move the red cutoff to the blue (Al) or red (In). Regardless of the material (e.g. another choice is diamond) coupling the resulting photocathode to a device such as a micro-channel plate (MCP) is necessary to produce imaging. Based on advances we have made both in the production of p-type GaN photocathodes, diamond photocathodes, and read-outs of Si MCPs, we are on the verge of making high quality UV imaging systems for astronomy and other low-light level applications. However, the outstanding question is how to optimize the photo-cathode performance. In this paper we discuss this question in the context of our progress in making GaN-based photo-cathodes.

Original languageEnglish (US)
Pages (from-to)225-232
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Dec 1 2002
EventFuture EUV/UV and Visible Space Astrophysics Missions and Instrumentation - Waikoloa, HI, United States
Duration: Aug 22 2002Aug 23 2002


  • GaN
  • Photocathode
  • UV astronomy
  • Wide band-gap semiconductor

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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