Interfacial properties of Ga-doped ZnO thin films on Si

Abstract

Ga-doped ZnO films of thicknesses 3 to 500 nm were grown on Si at 200°C by pulsed-laser deposition in 10 mTorr of Ar. Sheet carrier concentration ns and mobility μ were measured at room temperature by the Hall effect and were fitted, respectively, to the equations n s (d)=n(∞)(d−δd) and μ(d)=μ(∞)/[1+d ∗ /(d−δd)] , where n(∞) is the predicted volume carrier concentration at d=∞ (the bulk value), δd is the thickness of the dead layer (if any), μ(∞) is the predicted mobility at d=∞ , and d ∗ is a figure of merit for the electrical properties of the interface. The fitted values of d ∗[/ sup] and δd were ∼ 23 and ∼ 11 nm , respectively. X-ray reflectance results were consistent with an ∼ 3-nm -thick interfacial layer of significantly lower density than that of bulk ZnO. X-ray photoelectron spectroscopy measurements showed an ∼ 10-nm -thick interfacial region in which the Ga peaks at ∼ 3.8% , well above the average value of 2.4% found in the bulk of the film.