Light receiving device

1. A light receiving device comprising:

a substrate;

a first contact layer disposed on a surface of the substrate;

a light receiving layer disposed on the first contact layer;

an intermediate layer disposed on the light receiving layer;

a wide-gap layer having a pn junction disposed on the intermediate layer;

a second contact layer disposed on the wide-gap layer; and

a groove formed for pixel isolation by removing the second contact layer and part of the wide-gap layer,

wherein the intermediate layer has a wider band gap than the light receiving layer,

wherein the wide-gap layer has a wider band gap than the intermediate layer, and

wherein the intermediate layer is made of a plurality of layers having different composition ratios, and the plurality of layers are arranged in an ascending order of band gaps from the light receiving layer to the wide-gap layer.

2. The light receiving device as claimed in claim 1 , wherein the wide-gap layer includes a p-type wide-gap layer and an n-type wide-gap layer, the n-type wide-gap layer serving as a bottom surface of the groove.

3. The light receiving device as claimed in claim 1 , wherein light incident on an opposite surface of the substrate is detected.

4. The light receiving device as claimed in claim 1 , wherein the light receiving layer includes InGaAs, and the intermediate layer includes InGaAsP, with the wide-gap layer including InP.

5. The light receiving device as claimed in claim 1 , wherein a side surface of the wide-gap layer situated at a sidewall of the groove is covered with a passivation film made of SiN or SiON.

6. The light receiving device as claimed in claim 1 , wherein the first contact layer is an n-type contact layer, and the second contact layer is a p-type contact layer.

7. The light receiving device as claimed in claim 1 , wherein pixels isolated by a plurality of said grooves are arranged in a one-dimensional array or in a two-dimensional array.