Bandgap widening and behavior of Raman-active phonon modes of cubic single-crystalline (In,Ga)$_2$O$_3$ alloy films

TL;DR

This study investigates how Ga incorporation affects the electronic and vibrational properties of cubic (In,Ga)$_2$O$_3$ alloy films, revealing bandgap widening and phonon mode shifts through spectroscopic techniques.

Contribution

It provides a comprehensive analysis of the electronic and vibrational property changes due to Ga doping in cubic (In,Ga)$_2$O$_3$ films using multiple spectroscopic methods.

Findings

Ga incorporation causes a linear blueshift in the absorption onset

Phonon mode frequencies are sensitive to Ga content

Effective electron mass depends on electron concentration

Abstract

The influence of Ga incorporation into cubic In$_2$O$_3$ on the electronic and vibrational properties is discussed for (In$_{1-x}$,Ga$_x$)$_2$O$_3$ alloy films grown by molecular beam epitaxy. Using spectroscopic ellipsometry, a linear dependence of the absorption onset on the Ga content $x$ is found with a blueshift of up to 150 meV for $x = 0.1$. Consistently, the fundamental band gap exhibits a blueshift as determined by hard X-ray photoelectron spectroscopy. The dependence of the absorption onset and the effective electron mass on the electron concentration is derived from the infrared dielectric functions for a Sn doped alloy film. The influence of alloying on phonon modes is analyzed on the basis of Raman spectroscopic measurements. The frequencies of several phonon modes are identified as sensitive measures for the spectroscopic determination of the Ga content.