PHOTODIODE

PROBLEM TO BE SOLVED: To provide a photodiode capable of keeping a carrier running time short and carrying out a narrow band performance by which a high output is realized. SOLUTION: On an n-type semiconductor cathode layer 11, there are sequentially laminated a first semiconductor layer 12, a second semiconductor layer 13, and a third semiconductor layer 14, and an anode electrode 15 of low impurity concentration. A cathode electrode 16 is connected to a region on the semiconductor cathode layer 11 in which the first semiconductor layer 12 is not formed. It is determined that a band gap energy of the second semiconductor layer 13 is less than respective band gap energies of the semiconductor cathode layer 11, the first semiconductor layer 12, and the third semiconductor layer 14; and that the second semiconductor layer 13 acts as an optical absorption layer at the time of applying a reverse bias. A thickness of the second semiconductor layer 13 is not greater than that of the first semiconductor layer 12, and is more than near a thickness set as to optimize a tradeoff between previously requested band and efficiency. COPYRIGHT: (C)2006,JPO&NCIPI