MULTILAYER AVALANCHE PHOTODETECTOR

摘要

MULTILAYER AVALANCHE PHOTODETECTOR The avalanche region of a photodetector comprises layers (31,33,35,37) in which the bandgap is graded, with steps back from the wider gap to the narrower gap. The preferred carriers (electrons) are rapidly accelerated in the regions of the steps, so that the probability of an electron causing an impact ionization in the narrow-gap region just past each step is high. The non-preferred carriers (holes) undergo a comparatively uniform acceleration and are thus more likely to lose energy by optical phonon emission. They are therefore less likely to cause impact ionizations. The device noise is thus reduced. Also, the necessary bias voltage is reduced.