GaN Photocathodes for UV detection and Imaging

O. H.W. Siegmund*, A. S. Tremsin, A. Martin, J. Malloy, M. Ulmer, B. Wessels

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

33 Scopus citations


The nitride-III semiconductors, in particular GaN (band gap energy 3.5 eV), AlN (band gap 6.2 eV) and their alloys AlxGai1-xN are attractive as UV photo-convertors with applications as photocathodes for position sensitive detector systems. These can "fill the gap" in the 150-400nm wavelength regime between alkali halide photocathodes (<2000Å), and the various optical photocathodes (>4000Å, mutlialkali & GaAs). Currently CsTe photocathodes have fairly low efficiency (Fig. 1) in the 100nm to 300nm regime are sensitive to contamination and have no tolerance to gas exposure. We have prepared and measured a number of GaN photocathodes in opaque and semitransparent modes, achieving >50% quantum efficiency in opaque mode and ∼35% in semitransparent mode (Fig. 2). The GaN photocathodes are stable over periods of >1 year and are robust enough to be re-activated many times. The cutoff wavelength is sharp, with a rapid decline in quantum efficiency at ∼380-400nm. Application of GaN photocathodes in imaging devices should be feasible in the near future. Further performance improvements are also expected as GaN fabrication and processing techniques are refined.

Original languageEnglish (US)
Pages (from-to)134-143
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2003
EventUV/EUV and Visible Space Instrumentation for Astronomy II - San Diego, CA, United States
Duration: Aug 7 2003Aug 7 2003


  • Gallium Nitride
  • Photocathode
  • Photon counting
  • Ultraviolet

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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