Low-Cost Dopants for High Performance and Aqueous-Derived ZnO Thin-Film Transistors
Generally, alkali earth metal dopant, especially magnesium, is well known as a carrier suppressor of zinc interstitials or oxygen vacancies. However, we found the doping effect of alkali earth metals in ZnO matrix on the contrary. We reported alkali earth metal as new N-type dopants and discussed the alkali earth metal doping effects on ZnO semiconductors in terms of its crystallinity, morphology, interface charge trapping, XRD, and Hall measurement.4Using these alkali earth metal dopants, we demonstrated the magnesium or calcium doped ZnO TFTs with the dramatically improved the field effect mobility, on/off current ratio and bias stability. In addition, we proved that the increase in the carrier concentration was the dominant reason for the enhancement in the electron mobility of the alkali earth metal-doped ZnO TFTs.
Herein, we introduce magnesium and calcium as low-cost dopants for high performance and low temperature and aqueous-precursor ZnO thin film transistors (TFTs). Ca-doped ZnO TFTs exhibited excellent electrical performance with the field effect mobility of 5.02cm2/V∙s, on/off current ratio of 107and negligible hysteresis and highly stable TFTs were demonstrated. We believe that in-depth study of the morphology, electrical properties of alkali earth metal-doped ZnO films make a great contribution to next-generation high-performance TFTs for flexible, printed and transparent electronics.
(a) Mechanism of formation of aqueous ZnO, (b) transfer curves of TFTs based on ZnO doped with various alkali earth metals (Mg 0.002 mol%, Ca 0.1 mol%, Ca 0.2 mol%).
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