Light receiving element and a method of fabricating the same

Abstract

A light receiving element having excellent characteristics, including high sensitivity and high response speed, can be achieved by a light element comprising unit structures each having two pn junction semiconductor layers, and a lightly doped semiconductor layer having low impurity density, lower than those of the p-type regions and the n-type regions of the two pn junction semiconductor layers, and which is sandwiched between the two pn junction semiconductor layers. The p-type regions of the pn junction semiconductor layers are disposed opposite to each other on opposite sides of the lightly doped semiconductor layer, respectively, and the n-type regions of the pn junction semiconductor layers are disposed opposite to each other on the opposite sides of the lightly doped semiconductor layer, respectively. In a method of fabricating such a light receiving element, using controlled shutters or an ion beam apparatus, the layers are formed of optimum semiconductors, in an optimum thickness and in optimum impurity densities. In this structure, photogenerated carriers move mainly through the lightly doped semiconductor layer. Therefore, the lifetime of the carriers is increased, and the drift mobility of the carriers is enhanced, so that the light receiving element is able to function with a high sensitivity at a high response speed.