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- In2O3 (3)
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Institute
β-Ga2O3 (GaO) holds great promise in high-power applications. GaO is predicted to outperform the leading technologies based on SiC and GaN due to a three times higher calculated critical field strength. It has been identified that alloying with Al results in an almost linear increase in the bandgap between Ga2O3 (4.85eV) and Al2O3 (7eV). A critical issue in the bandgap engineering of GaO is maintaining reasonable electron mobility, which is low for the pure material (150cm2/V/S). This project aims to explore GaO by Al alloying, which allows tunable wide bandgaps for engineering material properties and at the same time maintains excellent crystal quality. PXRD and their Rietveld refinement on several AlGaO crystals indicate a preferential ordering of Al and Ga over octahedral and tetrahedral sites. The results of an SXRD study using synchrotron radiation addressing the surface structure of β-AlxGa2−xO3(100) substrates with x=0−0.25. Our results indicate that the GaO(100) surface is nearly bulk terminated and remains smooth up to 800°C and 10−5mbar of molecular oxygen.
Amorphous oxide semiconductors (AOS) and transparent conductive oxides (TCO) are today one of most attractive fields of research in many industrial products, like e.g. high definition, low cost, transparent, and flexible displays. We got the unique possibility to measure a-GIZO and a-SnOx thin films and compare their electronic properties with those of In2O3, Ga2O3, ZnO, and SnO2 single crystals. We use resPES to study the electronic properties. We report on the core levels, the VB PES data, partial Integrated Yield (pIY) and the XAS absorption data. From these we are able to derive the elemental ratio, the pDOS as well as the band scheme. At the O1s resonance we observe multiple Auger processes from which we deduce that a band of localized defect states is located between the Fermi energy and the CBM. The resonant profiles taken at the corresponding metal edges indicate that metal states are involved in the DOS.
We report on spectroscopic investigations on In2O3 single crystals. We focus on the detailed analysis of the O1s resonance profile by resonant photoelectron spectroscopy. We analyze the electronic structure and assign the O2p to build the valence band and both, O2p and In5s5p states to contribute to the conduction band (CB). We determine the partial density of states for the valence and CBs and find a strong hybridization of O2p and In5s states. This is deduced from constant final state spectra on the O-KLL-Auger over the O K-edge and In M4,5-edge and a comparison to the corresponding X-ray absorption spectroscopy data.We also identify several types of defects.
A broad band of oxygen derived defects is identified that extends throughout the gap. These are attributed to small polarons which cause an anti-resonance in the valence states around the O1s threshold. In addition, a separate Auger decay at resonance indicates the existence of localized charge transfer states which involves localized In5s5p states.
A spectroscopic comparison of IGZO thin film and the parent In2O3, Ga2O3, and ZnO single crystals
(2016)
We use resonant photoelectron spectroscopy at the Zn 2p, Ga 2p, In 3d, and O 1s absorption edges to report on the electronic properties of indium–gallium–zinc-oxide thin films. We also compare the data with the respective data of the corresponding single crystals In2O3, Ga2O3, and ZnO. We focus on the elemental composition and, in particular, find no evidence for oxygen deficiency. The In, Ga, and Zn absorption data at resonance can be used to analyze the conduction band states in detail. We deduce that a configuration interaction between d10s0 and d9s1states is of importance. We provided a novel mechanism in which configuration interaction induced gap states create both, extended unoccupied states around E F as well as localized occupied states within the gap.
We report on spectroscopic investigations on In2O3 single crystals. We focus on the detailed analysis of the O1s resonance profile by resonant photoelectron spectroscopy (resPES). From these we analyze the electronic structure and assign the O2p- and In5sp state to build the valence band and the conduction band in different contributions, respectively. This is deduced from constant final state spectra on the O-KLL-Auger along the O K-edge and In M4,5-edge and a comparison to the corresponding X-ray absorption spectroscopy data. We also identify several types of defects. A broad band of oxygen derived defects is identified in the valence band and extends throughout the gap. Small polarons are attributed to cause an anti-resonance in the constant initial states around the O1s threshold. In addition, an Auger decay separated by the O-KLL is present at O-K resonance and indicates the existence of localized charge transfer states which involves In5sp states. Finally, we are able to distinguish two different oxygen species from the resPES data. One corresponds to theintrinsic In2O3 structure and the other is a non-corresponding species.