| 摘要 |
This invention provides an APD which can reduce a dark current derived from a mesa surface. An APD 301 is provided with the semi-insulating substrate 1, a first mesa 101 having a first laminate constitution in which a p-type electrode layer 2, a p-type light absorbing layer 3A, a light absorbing layer 3B with a low impurity concentration, a band gap inclined layer 4, a p-type electric field control layer 5, an avalanche multiplier layer 6, an n-type electric field control layer 7A, and an electron transit layer 7B with a low impurity concentration are stacked in this order on a surface of the semi-insulating substrate 1, a second mesa 102 having an outer circumference provided inside an outer circumference of the first mesa 101 as viewed from the laminating direction and having a second laminate constitution in which an n-type electrode buffer layer 8A and an n-type electrode layer 8B are stacked in this order on a surface on the electron transit layer 7B side, and a depletion control region 11 that is provided in layers on the second mesa 102 side relative to the p-type electric field control layer 5, formed in an encircling portion 14 provided inside an outer circumference of the first mesa 101 and encircling an outer circumference of the second mesa 102, and prevents the encircling portion of the p-type electric field control layer 5 from being depleted when bias is applied. |
