Tuning the Ge(Sn) Tunneling FET: Influence of Drain Doping, Short Channel, and Sn Content

We present experimental results on the realization of p-channel mode Ge(Sn) heterojunction band-to-band tunneling field effect transistors. We investigate the influence of three device parameters (drain doping, channel length, and tunnel barrier height at source side) of the semiconductor body of the devices on the device performance. We achieve a complete suppression of the n-channel mode in p-type operating conditions by systematically reducing the p-type drain doping from 1·10²⁰ to 2 · 10¹⁷ cm^-3, examined in sample series A. In the second sample series B, we investigate the influence of a reduction of the channel length down to 15 nm on transistor performance. To improve the ON current I_ON without degrading the OFF current I_OFF, we introduce a 10-nm delta layer of a Ge_1-xSn_x alloy at the source/channel junction in the third sample series C. We demonstrate an improved ON current I_ON compared with the reference sample without a GeSn delta layer.