| 摘要 |
PURPOSE:To enable the improvement of the guard ring effect, without damaging the high speed response, by a method wherein a compound photo absorption layer is allowed to have the gradient of impurity concentration for the generation of a built-in electric field. CONSTITUTION:The n type InGaAs photo absorption layer 3 has an impurity concentration of approx. 5X10<17>(cm<-3>) at the interface between an n type InP buffer layer 2; however, the concentration then gradually decreases to approx. 1X10<16>(cm<-3>) at the interface between an n type InGaAsP photo absorption layer 4. In the presence of the gradient of impurity concentration in the layer 3 in such a manner, a depletion layer from the p-n junction in the photo receiving part LP does not come to extend, and the built-in electric field generates there in the direction shown by an arrow BN. As a result, the breakdown voltage of the p-n junction in the LP decreases; therefore it is possible to take the difference in withstand voltage between a p<+> type quard ring part 8 sufficiently. Since carriers generating in the layer 3 are accelerated and advance toward an n type InP carrier multiplication layer 5, the decrease in the high speed response can be inhibited. |
