| 摘要 |
PURPOSE:To improve the response speed by a method wherein an epitaxial layer of the same conductivity type and an epitaxial layer of the second conductivity type are laminated on a high concentration substrate of the first conductivity type, and the P-N junction due to both the epitaxial layers is made as the P-N junction as a photodiode. CONSTITUTION:The P type epitaxial layer 12 of a normal concentration (low concentration) at approx. 1-50OMEGA-cm is formed on the P<+> type substrate 11 of a high impurity concentration e.g. 0.1OMEGA-cm, further the N type epitaxial layer 3 is laminated, and the region of the N type epitaxial layer 3 is suitably devided by a P<+> type isolation region 2. The high concentration P<+> type substrate 11 under the P type epitaxial layer 12 serves to reduce the lifetime of minority carriers generated by the absorption of photons, and then eliminates the delay of the response time of minority carriers generated at this part. But, on the other hand, the minority carriers at this part do not contribute to the generation of photocurrent. Therefore, it is necessary to determine the thickness of the P type epitaxial layer by the balance between both. |
