Electron mobility in AlN from first principles

TL;DR

This study uses first-principles calculations to determine the maximum electron mobility in AlN, considering phonon and impurity scattering, and finds potential high mobility at low doping levels.

Contribution

The paper provides the first theoretical upper limits of electron mobility in AlN accounting for phonon and impurity effects, aligning with experimental data.

Findings

Piezoelectric acoustic phonon scattering dominates at room temperature.

Ionized impurity scattering reduces mobility significantly at high doping.

Potential mobility of 956 cm²/V·s at low dopant concentrations.

Abstract

Aluminum nitride is a promising ultra-wide band gap semiconductor for optoelectronics and power electronics. However, its practical applications have been limited by challenges with doping and achieving high electrical conductivity. Recent advances in crystal quality and defect control have led to improvements in experimentally measured mobilities. In this work, we apply first-principles calculations to determine the upper limits of the electron mobility in AlN as a function of temperature, doping, and crystallographic orientation. We account for the combined effects of electron scattering by phonons and ionized impurity to model doped systems, and examine both full and partial ionization conditions. Our results show that the piezoelectric interaction from the long-range component of the acoustic modes is the dominant source of electron-phonon scattering at room temperature. Ionized-impurity scattering starts to dominate scattering at dopant concentrations above $10^{16}$ cm$^{-3}$, reducing the mobility by more than an order of magnitude in the high doping regime. Our calculated Hall mobility values are in good agreement with experimental data for samples with comparable dopant concentrations. We also find that electron mobilities as high as $956$ cm$^2$/V$\cdot$s could be achievable at lower dopant concentrations.