High speed and high efficiency infrared photodetectors
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The increasing demand for telecommunication systems resulted in production of high performance components. Photodetectors are essential components of optoelectronic integrated circuits and fiber optic communication systems. We successfully used resonant cavity enhancement technique to improve InGaAs based p-i-n photodetectors. The detectors had 66% peak quantum efficiency at 1572 nm which showed 3 fold increases with respect to similar photodetector without resonant cavity. The detectors had 28 GHz 3-dB bandwidth at the same time. The bandwidth efficiency product for these detectors was 18.5 GHz, which is one of the best results for InGaAs based vertical photodetector. The interest in high speed photodetectors is not limited to fiber optic networks. In the recent years, data communication through the air has become popular due to ease of installation and flexibility of these systems. Although the current systems still operate at 840 nm or 1550 nm wavelengths, the advantage of mid-infrared wavelengths will result in the production of high speed lasers and photodetectors. InSb based p-i-n type photodetectors were fabricated and tested for the operation in the mid-infrared (3 to 5 µm) wavelength range. The epitaxial layers were grown on semi-insulating GaAs substrate by molecular beam epitaxy method. The detectors had low dark noise and high differential resistance around zero bias. Also the responsivity measurements showed 49% quantum efficiency. The detectivity was measured as 7.98×109 cm Hz1/2/W for 60 µm diameter detectors. Finally the high speed measurements showed 8.5 and 6.0 GHz bandwidth for 30 µm and 60 µm diameter detectors, respectively.