InGaAs/InP p-i-n photodiode with an extrinsic pad isolation structure

A pad isolation technique has been developed to separate the electrically extrinsic pad area from the intrinsic device area, thereby reducing the extrinsic capacitance and enhancing the frequency response in an InGaAs/InP p-i-n photodiode. In this technology, the lateral etching characteristics of the InGaAs and a pad layout with a narrow feed line are applied in the device fabrication. Two devices, one employing the pad isolation structure and the other a conventional pad structure, were fabricated to compare their frequency performances. More enhanced 3 dB bandwidth characteristics were demonstrated in the devices using extrinsic pad isolation. These results indicate that extrinsic pad isolation is an effective technique in removing parasitic components and fabricating high-speed photodiode.