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

Melville P. Ulmer; Bruce W. Wessels; Oswald H. W. Siegmund

doi:10.1117/12.459765

24 February 2003 Advances in wide-bandgap-semiconductor-based photocathode devices for low-light-level applications

Melville P. Ulmer, Bruce W. Wessels, Oswald H. W. Siegmund

Proceedings Volume 4854, Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation; (2003) https://doi.org/10.1117/12.459765
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

The basic requirement for an 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.

Citation Download Citation

Melville P. Ulmer, Bruce W. Wessels, and Oswald H. W. Siegmund "Advances in wide-bandgap-semiconductor-based photocathode devices for low-light-level applications", Proc. SPIE 4854, Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation, (24 February 2003); https://doi.org/10.1117/12.459765

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