UV-visible sensors based on polymorphous silicon

UV-visible imaging systems can be used for various applications, including homeland security systems and mobile phones. Compared to conventional CCD technology, CMOS-based active pixel sensors provide several advantages, such as high integration, low voltage operation, low power consumption and low cost. In this approach, we have recently developed a novel technology using polymorphous silicon. This new material, fully compatible with above-IC silicon technology, is made of nanometer size ordered domains embedded in an amorphous matrix. The quantum efficiency of detectors made of this nano-structured material reach up to 80% at 550 nm and 30% in the UV range, depending of the design and the growth parameters. Furthermore, a record dark current of 20 pA/cm² at -3 V for 5 μm square pixels has been reached, and the sensor is perfectly linear over more than 6 decades of photocurrent. In addition, this new generation of sensors is significantly faster than their amorphous silicon counterparts.