High gain photodetectors formed by nano/micromachining and nanofabrication

Recently available methods in highly anisotropic nano/micromachining and nanofabrication (N/MEMS) enable the fabrication of high gain photodetector structures in both vacuum and semiconductor optoelectronics. We show results on nanomachined microchannels formed in semiconductors which enable robust long life photomultiplier-like tubes scaling in diameters from less than 1 mm to 30 cm in diameter, in various shapes (like strips or hexagons) with very compact dimensions along the axis, well less than 1 cm in thickness. The gain lifetime exceeds 1 C per square cm, and the gains can exceed 9,000 per nanomachined channel. The photolithographically precise channels enable precision imaging. Because the base matrix is a purified semiconductor, very low self-radioactivity counts result, unlike Pb-glass MCP. Additionally, because of the absence of lead, as in lead-glass MCP, common vacuum photocathodes can be deposited directly on the throats of the microchannels. We also show deposition on the throats of the the microchannels B- doped diamond with a SE yield exceeding 100, for photon counting. We also discuss results on a photodetector using a method akin to field emission into silicon, giving an APD-like gain using the geometric shape of the electrodes rather than doping profiles to achieve a controllable high field avalanche- gain region, with a considerably lower noise than compensated doped APD, also as a result of a high field volume, the major noise source, reduced by about 1000 times compared to equivalent APD. This gain has been tested in single pixel formats using AFM tips as the basis for the detector, and exceeded 5,000 in Geiger mode. These high gain pixel-sized detectors can be formed into imaging chips or silicon-PMT-like gained pixel array devices. We discuss applications in a wide variety of scientific instrumentation.