Sharp-Switching CMOS-Compatible Devices with High Current Drive

During the last few decades, our lives have been changed dramatically by the unprecedented development of electronic devices, which become faster, more portable and less expensive, yet with more integrated functionalities. This progress was all driven by MOSFET downscaling, doubling the integration density of integrated circuits roughly every two years, as embodied in Moore's law. However, the scaling of the MOSFET is reaching a fundamental limit. The subthreshold swing (SS) of a MOSFET, which is a criterion characterizing the sharpness of the switching from /0FF to /0N, is limited by the thermal diffusion between source and drain to a value larger than 60 mV/decade of current at room temperature. This physical limit impedes the scalability of the supply voltage FDD of the MOSFET. In order to enable further scaling of the FDD, sharp-switching devices with low SS < 60 mV/dec are of great interest. Sharp-switching transistors using different operation mechanisms have recently been proposed, such as the tunneling FETs (TFETs) and feedback FETs (FB-FETs). The TFET current is carried by interband tunneling rather than source-drain diffusion, and thus can achieve SS < 60 mV/dec at room temperature.' However, due to the large bandgap EG of Si, the /0N of Si TFETs is typically 3-5 decades lower than that of a comparable MOSFET and the small SS is only obtained over a restricted current range.'" On the other hand, the FB-FET has been demonstrated to possess both extremely sharp switching and a high /ON-' The operation of the FB-FET utilizes the positive feedback between carrier flow and injection barriers formed by both positive and negative surface charge densities Qs generated in Si3N4 spacers