Electrical conductivity anisotropy of InGaZn3O6 single crystals by pressurized optical floating zone growth and its oxygen annealing effect

Large bulk single crystals of InGaZn3O6 (InGaO3(ZnO)3 or IGZO-13) have been successfully grown using an optical floating zone method under a flow of dry-air at high pressure. These crystals exhibit a distinct blue hue in their as-grown state, with notable enhancement in transparency attainable through O2 annealing. Comparative analysis with IGZO-11 reveals a substantial reduction in conductivity following O2 annealing. Moreover, a pronounced in-plane/out-of-plane conductive anisotropy ranging from 100 to 450 is observed, surpassing that of IGZO-11 under similar in-plane conductivity conditions. This increase in electrical conducting anisotropy is ascribed to the incorporation of ZnO blocks amid the two InO layers, aligned along the c axis. Based on these findings, it is concluded that the contribution of In-5s orbitals likely assumes a predominant role, surpassing that of other cations from an experimental standpoint.