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Proceedings Paper

GaN photocathodes for UV detection and imaging
Author(s): Oswald H. W. Siegmund; Anton S. Tremsin; Adrian Martin; James Malloy; Melville P. Ulmer; Bruce Wessels
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Paper Abstract

The nitride-III semiconductors, in particular GaN (band gap energy 3.5 eV), AlN (band gap 6.2 eV) and their alloys AlxGa1-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.

Paper Details

Date Published: 8 December 2003
PDF: 10 pages
Proc. SPIE 5164, UV/EUV and Visible Space Instrumentation for Astronomy II, (8 December 2003); doi: 10.1117/12.510429
Show Author Affiliations
Oswald H. W. Siegmund, Univ. of California/Berkeley (United States)
Anton S. Tremsin, Univ. of California/Berkeley (United States)
Adrian Martin, Univ. of California/Berkeley (United States)
James Malloy, Univ. of California/Berkeley (United States)
Melville P. Ulmer, Northwestern Univ. (United States)
Bruce Wessels, Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 5164:
UV/EUV and Visible Space Instrumentation for Astronomy II
Oswald H. W. Siegmund, Editor(s)

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