| 摘要 |
PURPOSE:To improve the frequency characteristic by reducing a CR time constant and, at the same time, by reducing a diffused carrier component occupied in a photoelectric current by a method wherein the concentration of an N-type epitaxial layer is decided after the concentration has been divided into the concentration suitable for a photodiode and the concentration suitable for a bipolar device. CONSTITUTION:The concentration of a carrier in an N-type epitaxial layer 2 formed on a substrate 1 is set to the concentration suitable for a depletion layer of a PIN photodiode A; in addition, this N-type epitaxial layer 2 is divided into more than one pi layers 2a, 2b by P-well layers 3; out of more than one pi layer, an N-well layer 2c is formed additionally in the pi layer 2b where a bipolar device B is to be formed; the concentration of the carrier is raised to a value suitable for the bipolar device B. If the operation of the PIN photodiode A is checked after this constitution, the concentration of the N-type epitaxial layer (pi layer 2a) at the part is set to the low concentration (10<13>-10<14>cm<-3>) suitable for the PIN photodiode A and the depletion layer is easy to extend; even when the thickness of the part is formed to be suitable for the bipolar device B, the depletion layer is extended to the substrate 1 irrespective of the thickness of the epitaxial layer 2. |
