Electron and Hole Mobility of SnO2 from Full-Band Electron-Phonon and Ionized Impurity Scattering Computations

TL;DR

This study computes the electron and hole mobilities in SnO2 considering electron-phonon and impurity scattering, revealing a high electron mobility consistent with experiments and a much lower hole mobility, highlighting the impact of effective mass differences.

Contribution

It introduces a detailed first-principles approach to calculate mobility in SnO2 beyond simple models, accounting for all energy and momentum dependencies of scattering rates.

Findings

Electron mobility is calculated as 265 cm2V-1s-1, matching experimental ranges.

Hole mobility is significantly lower at 7.6 cm2V-1s-1.

Polar optical phonon scattering dominates the mobility limitations.

Abstract

Mobility is a key parameter for SnO2, which is extensively studied as a practical transparent oxide n-type semiconductor. In experiments, the mobility of electrons in bulk SnO2 single crystals varies from 70 to 260 cm2V-1s-1 at room temperature. Here, we calculate the mobility as limited by electron-phonon and ionized impurity scattering by coupling the Boltzmann transport equation with density functional theory electronic structures. The linearized Boltzmann transport equation is solved numerically beyond the commonly employed constant relaxation-time approximation by taking into account all energy and momentum dependencies of the scattering rates. Acoustic deformation potential and polar optical phonons are considered for electron-phonon scattering, where polar optical phonon scattering is found to be the main factor which determines the mobility of both electrons and holes at room temperature. The calculated phonon-limited electron mobility is found to be 265 cm2V-1s-1, whereas that of holes is found to be 7.6 cm2V-1s-1. We present the mobility as a function of the carrier concentration, which shows the upper mobility limit. The large difference between the mobilities of n-type and p-type SnO2 is a result of the different effective masses between electrons and holes.