Si based tunnel field effect transistors: Recent achievements

Recent achievements of silicon based tunnel field effect transistors (TFETs) and remaining major challenges are overviewed. Particular emphasis is placed on the band to band tunneling (BTBT) junctions, the heart of the device. Dopant segregation from ion implanted ultrathin silicide contacts proved as viable method to achieve steep tunneling junctions. This avoids defect generation by direct implantation into the junction and thus minimizes the risk of trap assisted tunneling. The method was applied to strained silicon, specifically to nanowire array transistors. This enabled the realization of TFETs with fairly high currents and first complementary TFET inverters with sharp transitions and good static gain, even at very low drain voltages of V_DD = 0.2 V. These achievements suggest a considerable potential of TFETs for ultralow power applications. Some novel concepts, e.g. to enlarge the tunneling area by “line tunneling”, are addressed. A benchmarking figure summarizes the present status.