Interfacial properties of Ga-doped ZnO thin films on Si

Ga-doped ZnO films of thicknesses 3 to 500 nm were grown on Si at 200 degrees C by pulsed-laser deposition in 10 mTorr of Ar. Sheet carrier concentration n(s) and mobility were measured at room temperature by the Hall effect and were fitted, respectively, to the equations n(s)(d) = n(infinity) (d - delta d) and mu(d) = mu(infinity)/[1 + d* / (d - delta d)], where n(infinity) is the predicted volume carrier concentration at d - infinity (the bulk value), dd is the thickness of the dead layer (if any), mu(infinity) is the predicted mobility at d - infinity, and d* is a figure of merit for the electrical properties of the interface. The fitted values of d* and delta d were similar to 23 and similar to 11 nm, respectively. X-ray reflectance results were consistent with an similar to 3-nm-thick interfacial layer of significantly lower density than that of bulk ZnO. X-ray photoelectron spectroscopy measurements showed an similar to 10-nm-thick interfacial region in which the Ga peaks at similar to 3.8%, well above the average value of 2.4% found in the bulk of the film. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)