Novel Multistate Quantum Dot Gate FETs Using SiO2 and Lattice-Matched ZnS-ZnMgS-ZnS as Gate Insulators

Multistate behavior has been achieved in quantum dot gate field-effect transistor (QDGFET) configurations using either SiO _x -cladded Si or GeO _x -cladded Ge quantum dots (QDs) with asymmetric dot sizes. An alternative method is to use both SiO _x -cladded Si and GeO _x -cladded Ge QDs in QDGFETs. In this paper, we present experimental verification of four-state behavior observed in a QDGFET with cladded Si and Ge dots site-specifically self-assembled in the gate region over a thin SiO₂ tunnel layer on a Si substrate. This paper also investigates the use of lattice-matched high-κ ZnS-ZnMgS-ZnS layers as a gate insulator in mixed-dot Si QDGFETs. Quantum-mechanical simulation of the transfer characteristic (I _D–V _G) shows four-state behavior with two intermediate states between the conventional ON and OFF states.