Electron mobility of ultrathin InN on yttria-stabilized zirconia with two-dimensionally grown initial layers

An In-polar InN ultrathin film with high electron mobility was grown on an insulating yttria-stabilized zirconia (YSZ) (111) substrate via precise control of growth conditions for initial monolayers. It was found that the first several monolayers of InN on YSZ can be grown in a two-dimensional mode using extremely N-rich (ex-N-rich) conditions. Although the growth of more than several InN monolayers under these conditions results in rough surfaces, probably because of the suppressed migration of In atoms on the surface, the combination of ex-N-rich growth for the first few monolayers with subsequent conventional In-rich growth leads to the successful formation of InN films with smooth surfaces. The electron mobility of 11-nm-thick InN on YSZ with two-dimensionally grown initial layers was 170 cm(2) V-1 s(-1), which is much higher than the best reported value for InN ultrathin layers grown on GaN substrates. These results indicate that the structural quality of the InN/YSZ heterointerface and a smooth surface are inherently important for obtaining InN ultrathin films with good transport properties. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4776210]