Novel Photodetector Design Using Open Circuit Voltage For Mid-Wave Infrared Imagers

Strong motivation for low-cost infrared imaging devices over the past few years have given rise to advances in infrared detector technology, specifically in the mid-wave infrared (MWIR) region. With increasing demand for small pixel sizes and large format focal plane arrays (FPAs), the extreme complexity in realizing MWIR imagers is expected to increase in difficulty. In this work, a novel approach to provide improved infrared detection at high operating temperatures is proposed by integrating proven MWIR photovoltaic material and mature digital CMOS Image Sensor (CIS) technology in a resultant technology concept of an open circuit voltage photodetector (VocP). With this new approach to photon detection, the photosensitive material generates an open circuit voltage to control the drain current of a transistor. The drain current can then be considered the photocurrent in the proposed pixel design. The VocP design decouples the photocurrent from the pixel area, exploits the invariance of open circuit voltage to pixel dimensions, improves the detectors dark current, and results in higher sensitivity. The proposed approach also couples an infrared sensitive material to CIS technology that is well established and continues to be advanced for visible imagers. In this paper, initial research demonstrations and test results are presented to provide evidence of MWIR detection at high operating temperatures to prove the concept and modeling predictions for the sensitivity and dynamic range of VocP.