Ntt Electronics Corporation

Nippon Telegraph and Telephone Corporation

Yukihiro Hirota

Tadao Ishibashi

Seigo Ando

Yoshifumi Muramoto

In an electron-injection type APD, it is necessary to prevent a dark current increase and to secure the life time of the device. It is demanded to improve reliability of the APD with a lower production cost. With the InP buffer layer having an n-type doping region on the inside of a region defined by an optical absorption layer, a predetermined doping profile is achieved by ion implantation. Thus, electric field concentration in the avalanche multiplication layer is relaxed. Furthermore, a low-concentration second optical absorption layer is provided between the optical absorption layer and the avalanche multiplication layer. Responsivity of the optical absorption layer is maximized, and depletion of the lateral surface of the optical absorption layer is prevented; thus, electric field concentration is prevented. Preventing edge breakdown, the device improves its reliability.

Avalanche photodiode having doping region with monotonically increasing concentration distribution

An ultra high speed APD capable of realizing reduction in an operating voltage and quantum efficiency enhancement at the same time is provided. Under operating conditions APD, a doping concentration distribution of each light absorbing layer is determined so that a p-type light absorbing layer () maintains a p-type neutrality except a part thereof, and a low concentration light absorbing layer () is depleted. Moreover, a ratio between a layer thickness Wof the p-type light absorbing layer () and a layer thickness Wof the low concentration light absorbing layer () is determined so that W&#x3e;0.3 &#x3bc;m and a delay time of an element response accompanying a transit of carriers generated in the light absorbing layer by light absorption takes on a local minimum under a condition that a layer thickness W(=W+W) of the light absorbing layer is constant.

Avalanche photodiode

A photodiode has an optical absorption layer composed of a depleted first semiconductor optical absorption layer with a layer width Wand a p-type neutral second semiconductor optical absorption layer with a layer width W. The ratio between Wand Wis set such that the total carrier transit time &#x3c4;becomes minimum in the optical absorption layer. The photodiode can further include a depleted semiconductor optical transmission layer with a bandgap greater than that of the first semiconductor optical absorption layer, between the first semiconductor optical absorption layer and an n-type semiconductor electrode layer.

Growing community of inventors

Atsugi, Japan

Yukihiro Hirota