Gallium arsenide phosphide-gallium arsenide heterojunction photodetectors

Conventional pn homojunction photodetectors when used as microwave modulation detectors suffer from a disadvantage inherent in its construction, namely, the need for a top layer either p- or n-type. To reduce the absorption of the incident light in this layer, the junction must be located close to the surface with consequent degradation due to surface effects. Also, the diffusion effects reduce the speed of response.