We have found that there is more than one type of conducting carriers generated in LaAlO3/SrTiO3 heterostructures by comparing the sheet carrier density and mobility from optical transmission spectroscopy with those from dc-transport measurements. When multiple types of carriers exist, optical characterization dominantly reflects the contribution from the high-density carriers whereas dc-transport measurements may exaggerate the contribution of the high-mobility carriers even though they are present at low density. Since the low-temperature mobility determined by dc-transport in the LaAlO3/SrTiO3 heterostructures is much higher than that extracted by optical method, we attribute the origin of high-mobility transport to the low-density conducting carriers.
Seo, S. S. A., Marton, Z., Choi, W. S., Hassink, G. W. J., Blank, D. H. A., Hwang, H. Y., ... Lee, H. N. (2009). Multiple conducting carriers generated in LaAlO3/SrTiO3 heterostructures. Applied physics letters, 95(8), 082107-. https://doi.org/10.1063/1.3213390