Inverted, substrate-removed vertical Schottky diode optical detectors

The InGaAs metal-semiconductor-metal (MSM) photodetector has great potential as a high-performance component for future lightwave communication systems and opto-electronic integrated circuits (OEICs). Low capacitance, dictated by finger spacing, and high carrier drift velocity should result in GHz operating bandwidths. Efficient optical absorption to 1.7 /spl mu/m results in high responsivity at the wavelengths preferred for optical fiber communications, 1.3 and 1.55 /spl mu/m. Although significant efforts have been devoted to the realization of InGaAs MSM photodetectors, few devices have found their way into commercial or military products. Among the technical problems still hindering the practical incorporation of InGaAs MSMs into optical systems and networks are their high dark current and the slow response of photo-generated holes. High dark current results from low Schottky barrier heights and poor surface passivation. The problem is compounded for devices with submicron finger spacing since the surface electric fields are very high. Analysis of carrier dynamics shows holes generated deep in the depletion region can significantly degrade the high-frequency response. For these reasons we have chosen to investigate new designs for vertical Schottky diode detectors.