Screening and transport in 2D semiconductor systems at low temperatures

TL;DR

This paper develops analytical formulas and numerical calculations to explain the intrinsic metallic temperature dependence of 2D semiconductor systems' resistivity, emphasizing the role of screening, disorder, and material quality.

Contribution

It provides a theoretical framework for understanding the strong temperature dependence in high-quality 2D materials based on screening effects, with experimentally testable predictions.

Findings

Strong intrinsic temperature dependence arises from 2D screening properties.

High-mobility samples exhibit more pronounced metallic behavior.

Comparison shows 3D screening cannot produce similar temperature effects.

Abstract

Low temperature carrier transport properties in two-dimensional (2D) semiconductor systems can be theoretically well-understood within a mean-field type RPA-Boltzmann theory as being limited by scattering from screened Coulomb disorder arising from random quenched charged impurities in the environment. In the current work, we derive a number of simple analytical formula, supported by realistic numerical calculations, for the relevant density, mobility, and temperature range where 2D transport should manifest strong intrinsic (i.e., arising purely from electronic effects and not from phonon scattering) metallic temperature dependence in different semiconductor materials arising entirely from the 2D screening properties, thus providing an explanation for why the strong temperature dependence of the 2D resistivity can only be observed in high-quality and low-disorder (i.e., high-mobility) 2D samples and also why some high-quality 2D materials (i.e., n-GaAs) manifest much weaker metallicity than other materials. We also discuss effects of interaction and disorder on the 2D screening properties in this context as well as compare 2D and 3D screening functions to comment why such a strong intrinsic temperature dependence arising from screening cannot occur in 3D metallic carrier transport. Experimentally verifiable predictions are made about the quantitative magnitude of the maximum possible low-temperature metallicity in 2D systems and the scaling behavior of the temperature scale controlling the quantum to classical crossover where the system reverses the sign of the temperature derivative of the 2D resistivity at high temperatures.