A germanium photodetector array for the near infrared monolithically integrated with silicon CMOS readout electronics

Abstract Near infrared (NIR) detectors, operating in the 1.3– 1.6 μm region, are key elements in a number of applications ranging from optical communications to remote sensing. InGaAs and Ge are currently the materials of choice for the fabrication of NIR detectors due to their good absorption and transport properties. However, as the required performances increase (bit-rate in optical communications, number of pixels in imaging, etc.), it becomes more and more important to reduce the separation from detectors and driving/biasing and amplifying electronics, by integrating the two components on the same chip. We demonstrate an array of NIR detectors monolithically integrated with standard silicon CMOS readout electronics. The employed low temperature process allowed the integration of the detectors as the last step of chip fabrication. The integrated micro-system consists of a linear array of 120×120 μm 2 pixels, an analog CMOS multiplexer and a transimpedance amplifier. The chip exhibits a good photoresponse in the NIR, with responsivities as high as 43 V / W at 1.3 μm , dark currents of 1 mA / cm 2 and inter-pixel cross-talk better than −20 dB .