A silicon drift photodiode

A low-capacitance photodiode based on the principle of the solid-state drift chamber has been constructed and tested. The device is based on a cellular design with an anode at the center of each of five cells, allowing electrons liberated by ionization to drift up to 1 mm to the readout strip. Two designs were produced with p/sup +/ implant widths of 75 mu m and 85 mu m, respectively, using n-type material of 3.5-k Omega -cm resistivity. The opposite surface is a uniform p-type implant, features matching those of the other surface, and is unmetallized to ensure good photosensitivity. Results on the performance of the detector, including leakage current, capacitance, and drift properties, are presented and compared with simulation results.<
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