Polarity Dependence of Structural and Electronic Properties of Al2O3/InN Interfaces

We have fabricated Al 2 O 3 /InN heterostructures on yttria-stabilized zirconia (111) substrates and investigated their structural and electronic characteristics, putting special emphasis on the effects of the polarity of the InN films. We have found that In-polar InN (0001) films grow with atomically flat surfaces, which makes a striking contrast to the case of N-polar InN (000$\bar{1}$) films, where InN films show rough surfaces. High resolution X-ray photoelectron spectroscopy measurements have revealed that the Al 2 O 3 /In-polar InN interfaces are abrupt, although InO x interdiffused layers are formed at the Al 2 O 3 /N-polar InN interfaces. We have also found that the valence band offset of Al 2 O 3 /In-polar InN is 2.8 eV, while that of N-polar InN is slightly smaller, probably because the surface of In-polar InN is more resistant to the oxidizing atmosphere of the atomic layer deposition process used for Al 2 O 3 deposition.