| 摘要 |
PURPOSE:To form a guard ring part by one ion-implantation process by using a focused ion beam by a method wherein the carrier concentration in an inside region which is one region at a second p-n junction and which overlaps with a first p-n junction is made about three times the carrier concentration of an outside region at the second p-n junction. CONSTITUTION:The carrier concentration in an inside region which is one region at a second p-n junction and which overlaps with a first p-n junction is about three times the carrier concentration in an outside region at the second p-n junction; the carrier concentration is changing continuously in an intermediate region between the inside region and the outside region at the second p-n junction. By this structure,it is possible to suppress a voltage breakdown at a curved part at the edge of a guard ring, which has been a problem with a conventional structure of the single guard ring; it is possible to obtain the same effect as in the case of two kinds of guard rings by two ion-implantation processes. By this setup, the voltage breakdown is caused in a p<+> region before the voltage breakdown is caused at the curved part of the guard ring; it is possible to obtain a high-multiplication and high-performance APD (avalanche photodiode).
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