Single-Electron Signal Modulator Designed for a Flash Analog-to-Digital Converter

Abstract

We demonstrate a 4-bit flash analog-to-digital converter (FADC) composed of a single-electron signal modulator (SESM) with a capacitive voltage divider (CVD). In the CVD, we utilize the self-capacitance of floating metal islands, and hence, maximum input impedance can be realized with the CVD. We also analyze the characteristics of the CVD with stray capacitance. The signals from the CVD are detected by four single-electron transistors (SETs), and their outputs, processed at quantizers, represent gray-coded digital signals. We designed two kinds of layouts for the CVDs, and fabricated two samples for each layout by photolithography, electron-beam lithography, and the shadow evaporation of aluminum. Measurements were executed at approximately 30 mK. Four-bit FADC operation was successfully simulated using experimental results. We also discuss the possibility of higher resolution with our circuit configuration.