Modulation of electron transportation in amorphous and polycrystalline indium–zinc-oxide films grown by pulse laser deposition

Abstract

Amorphous and polycrystalline indium–zinc-oxide (IZO) transparent conductive films have been grown by pulsed laser deposition (PLD) technique using O2 and Ar as background gas, respectively. The evolution of surface morphology and crystalline structure of the IZO films have been discussed in the frame of the kinetic molecular theory by considering the different kinetic energy loss and the surface migration of impinging particles in Ar and O2 atmosphere, respectively. Hall measurements show that for amorphous IZO films the highest electron mobility can be as high as 51cm2/Vs with the electron concentrations (Ne) being 4.0×1019cm−3 and the resistivity being 3.1×10−3Ωcm. Temperature dependent Hall measurements indicate that when Ne is <1019cm−3 the dominant scattering mechanism is defect scattering, when Ne is in the range of 1019–1020cm−3 both the defects and the ionized impurity contribute to the carrier scatterings, and when Ne is >3.1×1020cm−3 the formation of a non-parabolic conduction band in IZO films plays the most important role in the carrier scattering. The variation of the optical band gaps in IZO films with Ne was addressed by taking account of both the Burstein–Moss shift and the band-gap-narrowing effects. Additionally, all the amorphous IZO films are highly transparent (transmission>85%) in the visible spectrum, which makes the IZO films suitable for transparent conducting applications.