3-D Confined SWS-FETs Combining Quantum Well and Quantum Dot Superlattice (QDSL)

Abstract

Quantum confinement in 3-D leads to novel multi-state larger fan-out carrier transport in quantum dot FETs. Single electron transistors (SETs) and quantum cell automata (QCA) devices are limited by the number of carriers in the transport channel, which affects the logic fan-out in sub-5nm integrated circuits. This paper presents several transport channel structures for overcoming this limitation. Layers with large bandgap discontinuities are used to confine carriers along channel length, between source and drain. These layers are formed with low energy gap Ge QDSLs and are used in several two-channel twin-drain n- and p-FETs in SWS configurations: (i) p-FET with coupled SiGe Quantum well (QW) and Ge Quantum Dot Superlattice (QDSL) channel, (ii) n-FET with upper and lower Ge QDSL channels, and (iii) p-FET with upper and lower Ge QDSL channels on n-on-pSi. The coupling of QW and QDSL channels or two Ge QDSL channels, in a spatial wavefunction switched (SWS) FET structure, not only ensures higher concentration of carriers but also multi-state/multi-bit operation. Circuit simulations of 2-bit NOR gate have used BSIM based analog behavioral model (ABM).