A UV Photodetector with Internal Gain Fabricated in Silicon on Sapphire CMOS

We report on a photodetector fabricated in silicon on sapphire (SOS) CMOS with a responsivity of 20,000 AAV at a voltage bias of 100mV for a 100mum². The transparent sapphire substrate enables backside illumination of the device for wavelengths ranging from only 150nm up to several microns. The device achieves its sensitivity by exploiting the internal amplification of an MOS transistor biased in subthreshold. The optimum channel doping of the device is determined through TCAD simulations of the device structure.