Design and operation of CMOS-compatible electron pumps fabricated with optical lithography

TL;DR

This paper presents CMOS-compatible electron pumps fabricated with optical lithography on SOI wafers, achieving quantized current sources with performance comparable to e-beam lithography devices, suitable for integration with cryogenic CMOS and quantum technologies.

Contribution

It introduces a novel fabrication method for electron pumps using standard CMOS processes, avoiding e-beam lithography and enabling scalable quantum device integration.

Findings

Achieved quantized current up to 300 MHz in non-adiabatic regime.

Demonstrated CMOS-compatible fabrication of electron pumps on 300 mm wafers.

Modeled charge trap effects impacting charge pumping.

Abstract

We report CMOS-compatible quantized current sources (electron pumps) fabricated with nanowires (NWs) on 300 mm SOI wafers. Unlike other Al, GaAs or Si based metallic or semiconductor pumps, the fabrication does not rely on electron-beam lithography. The structure consists of two gates in series on the nanowire and the only difference with the SOI nanowire process lies in long (40 nm) nitride spacers. As a result a single, silicided island gets isolated between the gates and transport is dominated by Coulomb blockade at cryogenic temperatures thanks to the small size and therefore capacitance of this island. Operation and performances comparable to devices featuring e-beam lithography is demonstrated in the non-adiabatic pumping regime, with a pumping frequency up to 300 MHz. We also identify and model signatures of charge traps affecting charge pumping in the adiabatic regime. The availability of quantized current references in a process close to the 28FDSOI technology could trigger new applications for these pumps and allow to cointegrate them with cryogenic CMOS circuits, for instance in the emerging field of interfaces with quantum bits.