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A team at the Army Research Laboratory has developed a new material stack to enhance the quantum efficiency in photodetectors. The patented technology is available via patent license agreement to companies that would make, use, or sell it commercially.
In general, desirable features of interest for photodetectors include improved response times and low noise; particularly in optical systems. One type of photodetector of particular interest for use in optical systems is the avalanche photodetector (APD). Avalanche photodetectors exhibit current gain due to avalanche multiplication.
Three ARL scientists have improved on the above features in APDs with a polar semiconductor layer formed as an initial layer of a photodetector. This deposition may be referred to as a polar window layer, comprising a transparent interface charge control layer. The layer has both a larger band gap than the absorption region of the photodetector and a different total polarization (spontaneous and/or piezoelectric) than the adjacent illuminated surface of the photodetector subassembly.
Resulting devices have the significant advantage that the discontinuity in polarization at the hetero-interface (between the polar window and the photodetector subassembly) induces an interface charge that offsets the initial surface/interface charge in the photodetector thereby suppressing the depletion layer and increasing the quantum efficiency of the detector at short wavelengths.
- This approach is distinctly different from putting solely an antireflective coating as antireflective coatings are generally not polar and do not induce a polarization charge at the interface.
- Businesses can commercialize the technology by licensing U.S. Patent 8,269,222 from the Army
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