| 摘要 |
<p>A sequential mesa type avalanche photodiode (APD) comprises a semiconductor substrate (1a, 1b) and a sequential mesa portion (10) formed on the semiconductor substrate (1a, 1b). In the sequential mesa portion (10), a plurality of semiconductor layers (2a, 2b, 3a, 4a, 4b, 5a, 5b, 6b, 12b, 13b, 14b, 15a, 16a), including a light absorbing layer (3a, 3b) and a multiplying layer (5b), are laminated by epitaxial growth. In the plurality of semiconductor layers (2a, 2b, 3a, 4a, 4b, 5a, 5b, 6b, 12b, 13b, 14b, 15a, 16a) , a pair of semiconductor layers (4a, 4b, 5a, 5b, 6b, 14b, 15a, 12b) forming a pn junction is included. The carrier density of a semiconductor layer (4a, 4b, 6b, 14a, 15a) which is near to the semiconductor substrate (1a, 1b) among the pair of semiconductor layers (4a, 4b, 5a, 5b, 6b, 14b, 15a, 12b) is larger than the carrier density of a semiconductor layer (5a, 5b, 14b, 12b) which is far from the semiconductor substrate (1a, 1b among the pair of semiconductor layers (4a, 4b, 5a, 5b, 6b, 14b, 15a, 12b). In accordance therewith, in the APD, light-receiving current based on movement of electrons and positive holes generated in the sequential mesa portion (10) when light is incident from the semiconductor substrate (1a, 1b) toward the light absorbing layer (3a, 3b) is larger at a central portion than at a peripheral portion of the sequential mesa portion (10). <IMAGE></p> |
