The electron mobility of In-Ga-Zn-oxide (IGZO) is known to be enhanced by higher In content. We theoretically investigated the mobility-enhancement mechanism by proposing an In-Ga-Zn-disorder scattering model for an In-rich crystalline IGZO (In1+xGa1−xO3(ZnO)m (0 < x < 1, m > 0)) thin film. The obtained theoretical mobility was found to be in agreement with experimental Hall mobility for a crystalline In1.5Ga0.5O3(ZnO) (or In3GaZn2O8) thin film. The mechanism specific to In-rich crystalline IGZO thin films is based on three types of Coulomb scattering potentials that originate from effective valence differences. In this study, the In-Ga-Zn-disorder scattering model indicates that the effective valence of the In3+ ions in In-rich crystalline IGZO thin films significantly affects their electron mobility.
-We have reported that the transistors having the c-axis-aligned crystalline (CAAC) In-Ga-Zn oxide (IGZO) show good performance. Recently, In-Sn-Zn Oxide (ITZO) has attracted much attention because of its high electron mobility, as well as IGZO. However, it has been reported that ITZO field effect transistors (FET) tend to have positive Vth (normally-on characteristics) and poor reliability compared with IGZO-FETs. We have reported that high-performance and high-reliability OS-FETs can be fabricated by using CAAC-IGZO, which has high crystallinity and has no clear grain boundaries, as an active layer. Therefore, we have fabricated CAAC-ITZO thin films to improve performance of ITZO-FETs by using CAAC-ITZO as an active layer. In addition, FETs employing CAAC-ITZO have better characteristics and reliability than FETs using nano-crystal ITZO. Furthermore, constant photocurrent method (CPM) measurement was carried out in order to estimate density of deep-level defect states caused by oxygen vacancies in oxide semiconductors. The results show that CAAC-ITZO has lower density of deep-level defect states than nano-crystal ITZO. We attribute the improvement in reliability of ITZO-FETs to a decrease in deep-level defect states of an ITZO active layer, as is the case with IGZO.
We used new In‐Ga‐Zn oxide composition (In:Ga:Zn = from 4:2:3 to 4:2:4.1) to fabricate bottom‐gate, top‐contact field‐effect transistors with high mobility and stability. Here we discuss these improvements in mobility and stability based on experiments and calculations. We succeeded in fabricating a 513‐ppi in‐cell‐type touch panel using this In‐Ga‐Zn oxide.
We developed a novel polymer-metal oxide composite which is suitable as a buffer layer for solution-processible OLEDs. The composite, which consists of vanadium oxide and an aminecontaining polymer, was fabricated by a sol-gel technique. It is possible to create Ohmic contact between the composite and electrodes, and this enabled the production of OLEDs with low driving voltage and high current efficiency.
We investigated In-Ga-Zn oxide films deposited by two types of sputtering methods: planar magnetron and facing-target. In crystallinity, we found that silicon diffused from SiO x prevents crystallization regardless of the sputtering method. In electrical property, we found that mobility of films deposited by facing-target sputtering less depends on carrier concentration.
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