N-type Sn substitution in amorphous IGZO film by sol-gel method: A promoter of hall mobility up to 65 cm2/V•s

Abstract

Indium gallium zinc oxide (IGZO) thin films with various tin (Sn) substitution contents were prepared on the glass substrate by using sol-gel spin coating. After Sn-doped IGZO precursor coatings were calcined at 550°C for 1 hr, the optical and electrical properties of IGZO thin films were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible spectroscopy (UV-Vis), Hall effect measurement, and X-ray photoelectron spectroscopy (XPS). With the chemical route, the film composition in the form of InGa(Zn1-xSnx)O4 (Sn-x-IGZO) can be well controlled to study the effect of Sn substitution. The results showed that all Sn-IGZO thin films were amorphous, had optical transmittance above 86%, and band-gap of 3.60-3.73 eV. The Sn-0.1-IGZO films with 89% optical transmittance had a carrier concentration of 3.48×1015 cm-3, mobility of 65 cm2/V•s, and electrical conductivity of 4.30×10-2 S/cm, where there was the 15-fold increase in mobility and 2,100-fold increase in conductivity, as compared to the undoped IGZO. A well consistent defect mechanism is proposed to explain the contradiction for more oxygen vacancies at higher Sn4+ content in equations.