| 摘要 |
PURPOSE:To attain high speed and high sensitivity without decreasing the break- down voltage and reducing remarkably the carrier concentration of the absorbing layer, by providing with a reflection region having a high reflection factor to incident light, on the side of the light absorbing layer opposite to the light- incident side. CONSTITUTION:Incident light is transmitted efficiently through a non-reflective coating 6 into a photo diode, and a portion of the incident light is absorbed by a light absorbing layer 3 to be converted into electron-positive hole pairs. Since the light absorbing layer has a half thickness as compared with prior arts, the transmitted light, not being absorbed, reaches a distributed reflector 5. Since the distributed reflector 5 has respective layer thicknesses and a cycle set so that it represents a high reflection factor to the incident light, the light is reflected here and is again incident into the light absorbing layer 3 to be absorbed. Thus the incident light into the photo diode can be converted into electron-positive hole pairs at a high quantum efficiency. The resulted positive holes undergo avalanche amplification at a high electric field region in the N<-> InP layer 1 and are taken out as an external current at a high gain. |
