Germanium imaging sensor

The development and evaluation of a germanium imaging sensor is described. The sensor, comprised of an electron-beam-scanned photodiode array, was designed for air-glow operation. Surface- barrier photodiode arrays were developed for optimized imaging, and their processing provided a powerful technique for preserving the characteristic properties of high-resistivity germanium by limiting the maximum processing temperature to 540°C. Photodiode-array processing was developed to a high degree of sophistication, but for satisfactory imaging using airglow illumination, additional development is required to improve the electron-beam characteristics of the tube, array cooling, and video amplifier. The best sensor had a quantum efficiency of ≥67.4 percent at 1.55 μm and 90°K for an absolute sensitivity of 0.84 A/W.