Silicon Single-electron Devices for Logic Applications

Abstract

The single-electron device (SED) is drawing a lot of attention for future large-scale integration because of its low-power nature and small size. We have developed a novel method called pattern-dependent oxidation (PADOX) for fabricating small Si single-electron transistors (SETs) and used it to make many kinds of SEDs. One of the most primitive and important SEDs that we have demonstrated is a quasi-CMOS type inverter that has voltage gain larger than unity. The inverter utilizes a SET as a switch, although it acts as both p-type and ntype switches. In addition, SETs have two unique features that conventional transistors do not have. One is multiinput gates capability, and the other is oscillatory conductance as a function of gate voltage. We have exploited these features to achieve complicated functions, such as an adder and a multiple-valued memory. In addition, we have developed a single-electron CCD that enables us to manipulate a single electron without tunnel capacitors. The device utilizes small Si-wire MOSFETs connected in series, and an elementary charge can be transferred like in a CCD.