Design of GeSn-Based Heterojunction-Enhanced N-Channel Tunneling FET With Improved Subthreshold Swing and ON-State Current

We design a heterojunction-enhanced n-channel tunneling FET (HE-NTFET) employing a Ge_1−xSn_x/Ge_1−ySn_y ( ) heterojunction located in the channel region with a distance of from the source-channel tunneling junction. We investigate the impact of on the performance of HE-NTFETs by simulation. HE-NTFETs achieve a positive shift of , a steeper subthreshold swing (SS), and an enhanced compared with homo-NTFETs, which is attributed to the modulating effect of heterojunction on band-to-band tunneling (BTBT). At a supply voltage of 0.3 V, 304% enhancement is demonstrated in the Ge_0.92Sn_0.08/Ge_0.94Sn_0.06 HE-NTFET with a 4 nm over Ge_0.92Sn_0.08 homo-NTFET due to the steeper average SS. The impact of Sn composition on the performance of HE-NTFETs is also studied. As we increase the difference in Sn composition across the heterojunction, and SS of HE-NTFETs are improved due to the increase in band offsets at the Ge_{1−xSnx/Ge1−ySny interface, which leads to the enhanced modulating effect of heterojunction on BTBT.}