Lateral high-speed metal-semiconductor-metal photodiodes on high-resistivity InGaAs

First results are presented on the fabrication and characterization of MSIM photodetectors on high-resistivity Fe-doped InGaAs. The acronym MSIM refers to the fact that the active layer of the photodiodes consists of a semi-insulating (SI) photoabsorbing semiconductor layer. Metal-semiconductor-metal (MSM) photodetectors on high-resistivity InGaAs with a lateral planar structure have been fabricated and characterized. The detectors formed exhibit a low capacitance (<50 fF), a very fast response (>14 GHz), a dark current of about 250 nA at a bias voltage of 10 V, and an external quantum efficiency of 20% at 1.3 mu m. The dark current values of the MSIM devices are only a factor of three larger than the values for MSM photodetectors based on a technologically complex AlInAs/InGaAs superlattice. This result indicates that the Fe doping of the photoactive InGaAs layer yields a significantly increased Schottky barrier. The fabrication of MSM photodetectors on high-resistivity InGaAs is demonstrated. Laterally structured photodiodes are formed with interdigitated contact fingers. The devices show a high response bandwidth and are suitable for high-speed applications.<
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