Patent ID: 8101940

Claim:
A photodetector comprising: a first conductivity-type InAs substrate; a first conductivity-type InAs buffer layer formed on the first conductivity-type InAs substrate; a first conductivity-type InAs light absorbing layer formed on the first conductivity-type InAs buffer layer; a cap layer formed on the first conductivity-type InAs light absorbing layer, and made from InAs X P Y Sb 1-X-Y (X≧0, Y>0) containing In and at least two of As, P, and Sb; a first inorganic insulating film formed on the cap layer, and having an opening portion in a deposition direction; a second conductivity-type impurity semiconductor region formed by diffusing a second conductivity-type impurity from the opening portion of the first inorganic insulating film, and reaching from the cap layer to an upper layer of the first conductivity-type InAs light absorbing layer; and a second inorganic insulating film formed on the first inorganic insulating film and on the second conductivity-type impurity semiconductor region.