Heteroepitaxy of Ga2(1-x)In2xO3 layers by MOVPE with two different oxygen sources

• Published in: Crystal research and technology (1979) Vol. 49; no. 8; pp. 552 - 557
• Main Authors: Baldini, M., Gogova, D., Irmscher, K., Schmidbauer, M., Wagner, G., Fornari, R.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.08.2014
• Subjects: Ga2O3; In2O3; metal organic vapor phase epitaxy; thin films; transparent semiconducting oxides
• ISSN: 0232-1300; 1521-4079
• DOI: 10.1002/crat.201300410

Ga2(1‑x)In2xO3 epitaxial layers have been grown on (0001) Al2O3 substrates by metal organic vapour phase epitaxy (MOVPE). The process parameters were optimized and the effects related to the use of two alternative oxygenation sources like O2 and H2O were studied. Different In content x [x = In/(In + Ga)] were investigated in order to determine the In solubility limit in β‐Ga2O3. By using pure O2 during the growth, the In amount detected in the layers increased linearly with the flux of In precursor injected into the reactor, but the X‑ray diffraction patterns showed the presence of In2O3, in addition to β‐Ga2O3, for every In content. The second phase formation was confirmed by a double step feature placed at the absorption edge in optical transmission spectra, compatible with the presence of the two materials. With H2O as an oxygenation source, no In2O3 phase was observed up to x∼0.25. The growth of the mixed Ga2(1‐x)In2xO3 phase was confirmed by XRD spectra, wherein the β‐Ga2O3‐related peaks shifted at lower 2θ angles as expected from the substitution of Ga3+ ions with bigger In3+ ones. The variation of bandgap was confirmed by optical transmittance measurements, which showed a red shift of the absorption edge corresponding to In incorporation. The subject of this paper is the epitaxial growth of thin films of gallium‐indium oxide (Ga2(1−x)In2xO3), a transparent semiconducting oxide. The effects related to the use of oxygen and water as oxygenation sources were investigated. With oxygen, independently from the amount of In incorporated in the layers, phase separation of the two binary oxides was observed. With water, on the other hand, no In2O3 phase occurred up to x∼0.25, and the layers showed improved surface morphology.