AVALANCHE PHOTODIODE WITH DOUBLE GUARD RING

摘要

6446-320 An avalanche photodiode has a light absorbing semiconductor layer and an avalanche gain semiconductor layer having a bandgap greater than that of the light absorbing semiconductor layer. A first p-n junction having a substantially p+-n junction is selectively provided in the avalanche gain semiconductor layer. A second p-n junction having a substantially graded p-n junction surrounds the periphery of the first p-n junction. A third p-n junction having a substantially graded p-n junction surrounds the periphery of the second p-n junction. A specific feature of the invention is that the second p-n junction is positioned deeper from the upper surface than the first p-n junction and the third p-n junction is positioned closer to the upper surface than the second p-n junction. The photodiode of the invention is capable of achieving sufficient and uniform avalanche gain in a stepwise p-n junction region corresponding to its light receiving region before a voltage breakdown occurs in its guard ring. 54907/84