| 摘要 |
PURPOSE:To obtain an avalanche photodiode which reduces an operating voltage without increasing an excessive noise with preferable guard ring effect by reducing the thickness of the bottom of a region forming a substrate and a P-n junction. CONSTITUTION:An n type InGaAs or InGaAsP photoabsorbing layer 22, an n type InP intermediate layer 23', and an n<-> type InP window layer 23 are grown on an n<+> type InP substrate 21, beryllium is implanted on the substrate, thereby forming a p-n junction. Cd is diffused to form a p<+> type region 24, and an AuZn electrode 27 and an AuGe electrode 28 are formed. A p type region 25 for generating a guard ring effect is presented on the bottom of the light receiving region 24, but since the thickness is smaller than the width of the periphery, the expansion of a depletion layer is suppressed by the region 24, and sufficiently large breakdown voltage difference can be secured as compared with the periphery. Since the maximum electric field intensity can be reduced, the operating voltage can be, if the excess noise can be reduce to the same level, reduced by half as compared with the conventional one. |
