Corundum-structured α-phase Ga2O3-Cr2O3-Fe2O3 alloy system for novel functions

We propose a novel alloy system of oxide semiconductors promising for unique multifunctions, the corundum structured Ga2O3-Cr2O3-Fe2O3 alloys on sapphire substrates. With this system the optical band gap can be widely tuned from 2.2 to 5.3 eV while keeping the acceptable lattice mismatch. A key issue was to fabricate alpha-Ga2O3 thin films, which has been recognized as a sub-stable phase and there is a strongly tendency of growing at beta-Ga2O3 with traditional growth techniques, so the use of mist chemical vapor deposition (CVD) successfully overcame this problem and allows the growth of highly crystalline alpha-Ga2O3. Following to our previous achievements of exploring the corundum structured Ga2O3-Fe2O3 alloys, in this paper we have shown the growth of alpha-Cr2O3 thin films and a-phase Ga2O3-Cr2O3 alloys. The results encourage the evolution of the Ga2O3-Cr2O3-Fe2O3 alloys but the existing problem of low solubility in water and high decomposition energy of the Cr precursor presently used, chromium acetylacetonate [(C5H8O2)(3)Cr], should be overcome for accelerated research of this promising new alloy system. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim