Device performance tuning of Ge gate-all-around tunneling field effect transistors by means of GeSn: Potential and challenges

In this paper we report experimental results on the fabrication and characterization of vertical Ge gate-all-around p-channel TFETs, utilizing GeSn as a channel material. Through two sample series, the potential and challenges of implementing the low-band gap material GeSn are reviewed. It is verified that ION can be effectively enhanced by increasing the Sn-content in the GeSn-channel, due to increasing tunneling probabilities. Further it is found that when limited to a 10 nm δ-layer, Ge0.96Sn0.04 is most beneficial for ION when positioned inside the channel as opposed to in the source, with a maximum of ION = 180 µA/µm at VDS= −2 V and VG = −4 V. Enhanced leakage currents (IOFF), which also degrades the subthreshold swing (SS), is a consequence of a smaller band gap and enhanced defect densities, and represent key challenges with implementing GeSn.