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Annealing-induced solid phase crystallization of In₂O₃:H leads to a significantly improved electron mobility, which is confirmed by Hall measurements. Indium hydroxide dehydroxylation occurs in In₂O₃:H during annealing, which is well responsible for the structural transformation and a high electron mobility with a decreased carrier concentration in crystallized In₂O₃:H. A significant decrease in the intensity of occupied gap states is observed in crystallized In₂O₃:H, possibly due to a decrease in carrier concentration. Doped In₂O₃ variants have been found to have a quite deeper allowed transition level below the valence-band edge than undoped In₂O₃, which in particular applies to crystallized In₂O₃:H, but most likely attributed to a change of the crystal structure upon annealing and/or a different O 2p-In 4d coupling near the VBM compared to amorphous In₂O₃:H.
To well understand the interface properties of Ag/In₂O₃:H upon annealing, a thin Ag film was grown on the In₂O₃:H substrate and annealed in vacuum up to 300 °C. During annealing, the potential Ag diffusion into the bulk In₂O₃:H and/or a change of an annealing-induced Ag topography (i.e., cluster formation) occurs, with a small Ag oxidation (i.e., Ag₂O and AgO). With Ag deposition, an initial downward band bending of (0.11±0.05) eV was present in In₂O₃:H, attributed to a Schottky contact formed at the Ag/In₂O₃:H interface. Upon annealing, the downward band bending reduces gradually, and the Schottky-barrier height at the Ag/In₂O₃:H interface also decreases.
A thickness series of the individual materials on the respective “substrate” (i.e., MnS/Si, GaN/MnS, and ZnO/GaN) was epitaxially grown on Si (100) wafer, and the interfacial chemistry and energy-level alignment at the respective interfaces are examined using photoelectron spectroscopy. At the MnS/Si interface, an interface-induced band bending (IIBB) appears in Si, which of values are found to be (0.15±0.07) and (0.23±0.07) eV for 4 and 15 nm MnS/Si stacks, respectively. The MnS/Si heterointerface shows a type-II (staggered) band lineup with a VBO of (-0.37±0.10) eV and the corresponding CBO of (2.27±0.10) eV. For the GaN/MnS interface, a significant diffusion of Mn into the GaN layer takes place during GaN deposition. In addition, an interface-induced band bending (IIBB) by ~0.30 eV is observed in MnS. The GaN/MnS interface shows a type-II (staggered) band lineup with a VBO of (1.46±0.10) eV and the corresponding CBO of (-1.09±0.10) eV. At the ZnO/GaN interface, a significant N diffusion from GaN into ZsnO takes place, i.e., Zn-N bonds, when ZnO is grown on the GaN layer. Also, an interfacial oxide (GaOx) layer was formed during ZnO deposited on GaN films. The ZnO/GaN heterointerface shows a type-II (staggered) band lineup with a VBO of (2.48±0.10) eV and the corresponding CBO of (-2.50±0.10) eV, respectively.