Proceedings PaperMetal-semiconductor-metal photodetector with a-Ge:H absorption layer for 1.55um optical communication wavelength
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Metal-Semiconductor-Metal photodetectors (MSM-PDs) have been demonstrated with ease of fabrication, low capacitance, and faster responses compared to PIN photodetectors. Si and Ge are two of the CMOS compatible materials for sensing area of the photodetector. Ge, because of its higher mobility and absorption at 1.55μm wavelength is an attractive material of choice. In the outlined work, an interdigitated electrode MSM photodetector with a-Ge:H (amorphous-Ge:hydrogenated) as the sensing material has been recognized as a promising candidate for near infrared photodetection. Hydrogenating Ge generally helps improve material characteristics because it increases life time of photocarriers. Ge was sputter deposited with different H2 concentrations of 0%, 5%, 10%, 15%, and 25% in the plasma gas. The highest hydrogen concentration showed the highest responsivity among other detectors showing that hydrogen helps to reduce the number of defects within the a-Ge film and therefore increase the life time of carriers. Results show that highest photocurrent belongs to a sample with 25% H2 concentration in the plasma with a responsivity of 2mA/W and dark current of 11.6μA at 5v for a device area of 95×110 (μm)2.