Solar Blind AlGaN Photocathode

NanoSciences Corporation

Oxford, CT

The ternary III-V semiconducting compound AlxGa1-xN is an attractive material system for ultraviolet detector applications. The long wavelength cut-off can be varied from 365 to 200 nm, making it ideal for solar-blind photocathode applications.

• The GaN materials developments and processing techniques clearly showed the feasibility of the III-V nitride materials as robust photocathodes that could be processed to atleast QE or 25% at 254 nm.
• Technical goal of demonstrating the technical feasibility of the AlxGa1-xN family of photocathode materials has been met on the x=0 side of the composition range.
• NanoSciences is also working to extend these results to incorporation of the GaN and eventually InGaN into miniature surface mount photomultipliers for applications in medical imaging such as future time-of-flight positron emission tomography machines that will revolutionize early detection of diseases such as Alzheimers, Parkensons and various cancers.

• The commercial applications for near UV photocathodes based on III-V nitride materials include medical imaging, biological imaging and radiation detection. There is currently great interest in functional imaging with radionuclides, driven by new clinical applications using positron emission tomography.
• Other applications for the III-V nitride photocathode technology include defense applications as solar-blind photodetectors, detection and identification of radioactive materials.

• The number of potential applications for III-V nitride based photocathode materials is significant especially for NASA in advanced UV detection technology for future NASA missions.
• Photocathodes have been widely used as photoconvertors for space based detection employing microchannel plate detectors, from the near UV through the X-ray regimes for imaging and spectroscopy for example in ALEXIS, ORFEUS, SOHO STIS, FAUST, HUT, ROSAT, AXAF, EUVE, ACE, SAMPEX, IMAGE, FUSE, TIMED, ROSETTA, COS and GALEX.
• As specifically identified in the recent NASA UV/Visible detectors roadmap report and Hubble Space Legacy workshop, improving the detection quantum efficiency is a key issue for support of future mission viability, cost effectiveness, performance and reliability.

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Curator: SBIR Support                   6/22/05