Characteristic of hydrogenated Ga-doped ZnO films grown by DC magnetron sputtering using H_2/Ar gas

摘要

We report characteristics of sputtered Ga-doped ZnO films grown in pure Ar (Ar-films) and H_2/Ar gas mixture (H_2/Ar-films). With increasing water partial pressure (P_(H2O)), the resistivity of Ar-films significantly increased due to the decrease in both free carrier density and Hall mobility. The transmittance in the wavelength region of 300-400 nm for the films also increased with increasing P_(H2O). However, no significant P_(H2O) dependence of the electrical and optical properties was observed for H_2/Ar-films. Secondary ion mass spectrometry analysis revealed that hydrogen concentration in the Ar-films increased with increasing P_(H2O), indicating that the origin of the incorporated hydrogen is attributed to the residual water vapor in the coating chamber. On the contrary, the hydrogen concentration in H_2/Ar-films was almost constant irrespective of P_(H2O) and the concentration is obviously higher than that of Ar-films, indicating that the hydrogen primarily comes from H_2 gas and the adsorption species due to H_2 gas preferentially adsorb to the growing film surface over residual water vapor. Consequently, the effect of P_(H2O) on the crystal growth was significantly reduced by H_2 gas introduction, resulting in stability improvement.