Controlling gate-to-island coupling capacitance for elevated temperature operation of a multiple-valued memory using a single-electron transistor

摘要

In our multiple-valued (MV) memory, MV signals are obtained as an oscillating output of a single-electron transistor (SET) reading the amount of stored charges in the memory node. This is achieved by cancellation method, which takes into the account coupling capacitances (CCs) between side-gate (or substrate gate) and island electrode of SET. At temperatures above 13K, however, CCs become bias dependent due to carrier activation in Si substrate. It is shown that it is necessary to (1) use heavily-doped substrate to keep substrate-island CCs constant and (2) finely pattern the heavily-doped substrate to suppress the screening of the island by the substrate, to control CCs for elevated temperature memory operation.