Electron effective mass in unintentionally doped In$_{0.33}$Ga$_{0.67}$N determined by mid-infrared optical Hall effect

TL;DR

This study measures the electron effective mass in unintentionally doped In0.33Ga0.67N using mid-infrared optical Hall effect, finding nearly isotropic values and discussing band nonparabolicity effects.

Contribution

First determination of electron effective mass in In0.33Ga0.67N via optical Hall effect, including analysis of anisotropy and band nonparabolicity influences.

Findings

Electron effective mass is approximately 0.205 m0 perpendicular to c-axis.

No significant anisotropy detected within 7% upper limit.

Electron mobility parameters are anisotropic, consistent with previous wurtzite studies.

Abstract

Mid-infrared optical Hall effect measurements are used to determine the free charge carrier parameters of an unintentionally doped wurtzite-structure $c$-plane oriented In$_{0.33}$Ga$_{0.67}$N epitaxial layer. Room temperature electron effective mass parameters of $m^{*}_{\bot}=(0.205 \pm 0.013)~m_0$ and $m^{*}_{\parallel}=(0.204 \pm 0.016)~m_0$ for polarization perpendicular and parallel to the $c$-axis, respectively, were determined. The free electron concentration was obtained as $(1.7 \pm 0.2)\times 10^{19}~$cm$^{-3}$. Within our uncertainty limits we detect no anisotropy for the electron effective mass parameter and we estimate the upper limit of the possible effective mass anisotropy is 7$\%$. We discuss the influence of band nonparabolicity on the electron effective mass parameter as a function of In content. The effective mass parameter is consistent with a linear interpolation scheme between the conduction band mass parameters in GaN and InN when the strong nonparabolicity in InN is included. The In$_{0.33}$Ga$_{0.67}$N electron mobility parameters were found to be anisotropic supporting previous experimental findings for wurtzite-structure GaN, InN, and Al$_{x}$Ga$_{1-x}$N epitaxial layers with $c$-plane growth orientation.