Tunneling field effect transistors based on in-plane and vertical layered phosphorus heterostructures

Tunneling field effect transistors (TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here, we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous (beta-P and delta-P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio (PVR) when the intrinsic region length is near zero. Compared with the in-plane TFET based on beta-P and delta-P, better performance with a higher on/off current ratio of similar to 10(6) and a steeper subthreshold swing (SS) of similar to 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of the beta-P and delta-P layers in the in-plane and vertical heterostructures.