Bandgap widening and behavior of Raman-active phonon modes of cubic single-crystalline (In,Ga)_2O_3 alloy films

摘要

The influence of Ga incorporation into cubic In_2O_3 on the electronic and vibrational properties is discussed for (In_(1-x),Ga_x)_2O_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 150meV for x=0.1. Consistently, the fundamental bandgap 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.