AVALANCHE PHOTODETECTOR UTILIZING AN A-C COMPONENT OF BIAS FOR SUPPRESSING MICROPLASMAS

摘要

1,228,841. Avalanche breakdown devices. WESTERN ELECTRIC CO. Inc. 16 May, 1968 [18 May, 1967], No. 23213/68. Heading H1K. Localized microplasma breakdown is inhibited in semi-conductor devices operating in the avalanche mode by use of a bias which varies periodically between that of avalanche operation and a value less than that required for avalanche breakdown. The amplitude is such that at the minima a high turn off probability for microplasma is achieved and the frequency high enough to substantially inhibit breakdown due to microplasmas. In the embodiment a light-sensitive NP or NIP silicon photodiode formed by diffusion and epitaxial deposition steps is thus operated with a square wave or sinusoidal alternating bias voltage superimposed on a direct voltage bias. The alternating bias may have an amplitude of several hundred uA and a frequency above 200 kc/s. A 70-fold increase in sensitivity to light is achieved by this means, together with an improvement in signal/noise ratio.