Alloying In2O3 and Ga2O3 on AlN templates for deep-ultraviolet transparent conductive films by mist chemical vapor deposition

Abstract

We studied the phase diagram of (In x Ga1−x )2O3 thin films with a composition of x = 0 to 1 on Aluminum Nitride (AlN) templates grown using mist chemical vapor deposition. From X-ray diffraction results, we observed that the (In x Ga1−x )2O3 thin films exhibited three different single-phase crystal structures depending on the value of x: orthorhombic (κ)-(In x Ga1−x )2O3 for x ≤ 0.186, hexagonal (hex)-(In x Ga1−x )2O3 for 0.409 ≤ x ≤ 0.634, and body-centered cubic (bcc)-(In x Ga1−x )2O3 for x ≥ 0.772. The optical bandgap of (In x Ga1−x )2O3 was tuned from 3.27 eV (bcc-In2O3) and 4.17 eV (hex-InGaO3) to 5.00 eV (κ-Ga2O3). Moreover, hex-(In x Ga1−x )2O3 exhibited a wide bandgap (4.30 eV) and a low resistivity (7.4 × 10‒1 Ω·cm). Furthermore, hex-(In x Ga1−x )2O3 thin films were successfully grown on GaN and AlGaN/GaN templates. Therefore, hex-(In x Ga1−x )2O3 can be used in transparent conductive films for deep-ultraviolet LEDs.