Probing Band-Tail States in Silicon MOS Heterostructures with Electron Spin Resonance

TL;DR

This paper introduces an ESR technique to quantify shallow electron traps at Si/SiO2 interfaces in MOS devices, revealing differences in interface quality not detectable by mobility measurements.

Contribution

The study demonstrates a novel ESR-based method for assessing interface quality in MOS devices at low electron densities, providing a quantitative measure of shallow trap states.

Findings

ESR detects differences in interface trap densities between devices.

The method quantifies shallow trapped charges at low electron densities.

Significant variation in interface quality was observed despite similar mobilities.

Abstract

We present an electron spin resonance (ESR) approach to characterize shallow electron trapping in band-tail states at Si/SiO2 interfaces in metal-oxide-semiconductor (MOS) devices and demonstrate it on two MOS devices fabricated at different laboratories. Despite displaying similar low temperature (4.2 K) peak mobilities, our ESR data reveal a significant difference in the Si/SiO2 interface quality of these two devices, specifically an order of magnitude difference in the number of shallow trapped charges at the Si/SiO2 interfaces. Thus, our ESR method allows a quantitative evaluation of the Si/SiO2 interface quality at low electron densities, where conventional mobility measurements are not possible.