Rear entry photodiode

Abstract From the Canadian patent

A semiconductor photodiode includes a substrate of semi-insulating indium phosphide having a first layer of highly doped P type indium phosphide on a surface thereof. An active second layer of N type indium gallium arsenide is on the first layer and a third layer of N type indium gallium arsenide or indium phosphide is on the second layer. The third layer may be entirely more highly doped than the second layer or may have a highly doped region on its surface. A first contact is on the third layer and a second contact is on the first layer. A buffer layer of lightly doped N or P type indium phosphide may be provided between the first layer and the second layer.