| 摘要 |
A photodiode comprising a first layer of a relatively large forbidden band (e.g. 1.4 eV) in a p type of conductivity, wherein photons can be absorbed, thus creating pairs of electron-holes diffusing towards a second layer, said second layer having a forbidden band. (0.7 eV) that is approximately half of the first band. In that second layer of an n-type of conductivity each electron falls and creates by impact ionization a new pair electron-hole, thus producing an avalanche gain of 2. The phenomenon occurs theoretically with a zero bias voltage. In practice the photodiode operates with a bias voltage near zero. The two materials of the heterojunction are for instance In P (forbidden band: 1.4 eV) and Ga0.47 In 0.53 As (0.7 eV) providing crystalline networks perfectly matched.
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