| 摘要 |
A photodetector includes a compound semiconductor substrate including first and second elements and having a first energy band gap, a first conductivity type compound semiconductor light absorbing layer including at least one of the first and second elements and having a second energy band gap narrower than the first energy band gap, a transition layer having an energy band gap at least as wide as the second energy band gap and no wider than the first energy band gap disposed between and contacting the substrate and the light absorbing layer, at least a first recess extending through the substrate and the transition layer to the light absorbing layer, a second conductivity type region disposed in the light absorbing layer at the first recess, a first electrode disposed in the first recess in contact with the second conductivity type region, and a second electrode disposed in contact with the first conductivity type light absorbing layer.
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