Precise Tailoring of Charge Transport Characteristics in Zr and Hf Doped Indium Tin Oxide Thin Film Transistors

Zirconium and hafnium doped indium tin oxide (ITO) thin films are fabricated via atomic layer deposition (ALD) at 200°C from trimethylindium, tetrakis(dimethylamido)tin, tetrakis(dimethylamido)zirconium, and tetrakis(diethylamido)hafnium, using water as oxidant. Grazing incidence X-ray total scattering employing synchrotron radiation reveals a highly disordered structure with a short-range order, exhibiting correlation lengths of up to ∼13 Å. This is also reflected in high-resolution transmission electron microscopy, revealing an amorphous intermixed state of all constituting components. Increasing amounts of fully coordinated oxygen species with increasing amounts of dopant are evidenced by X-ray photoelectron spectroscopy analysis and attributed to zirconium and hafnium's ability to form strong oxygen bonds, and thereby suppressing the formation of oxygen vacancies. The Zr- and Hf-doped ITO thin films are integrated into thin-film transistor (TFT) devices to evaluate their suitability as semiconducting material. The electrical measurements reveal saturation mobilities (µ$_{sat}$) of 1.92–9.81 cm$^2$ V$^{−1}$ s$^{−1}$, with high current on/off ratios (I$_{On}$/I$_{Off}$) of 10$^6$–10$^8$. ... mehrThis study demonstrates the subtle influence of small amounts of Zr and Hf on TFT performance. This proves the ability to control the electrical behavior of TFT devices by controlled incorporation of dopants like Zr and Hf into their active channel layer.