High mobility undoped amorphous indium zinc oxide transparent thin films

Abstract

We investigated the amorphous region of the In2 O3 -ZnO material system. The composition dependence of the amorphous region was explored and the films exhibited an n -type semiconductor behavior with low resistivities in the range of 4× 10-4 -6.33× 10-4 Ωcm. These amorphous films have a very wide transmittance window range of 300-2500 nm, and the transmittance is higher than 85% in the fiber-optics telecommunication window of 1.30-1.55 μm. The band gap of amorphous films can be engineered from 2.66 to 3.05 eV, by varying the zinc (zinc+indium) atomic ratio. A monotonous decrease in mobility from 71. 6 to 59.4 cm2 V s was observed with an increase in zinc (zinc+indium) atomic ratio from 0.19 to 0.43 in the amorphous region. This trend was explained on the basis of percolation theory and overlap integral calculations. The effective mass of these amorphous films was calculated using the Drude model in the free-carrier absorption region and correlated with composition as well as the carrier concentration of the films. © 2005 American Institute of Physics.