Selective growth of N-polar InN through an in situ AlN mask on a sapphire substrate

Selective growth of N-polar InN by exploiting the ∼100° gap between the upper limits of the growth temperatures of In- and N- polarities has been introduced. An InN epilayer grown at a temperature in this gap on a sapphire substrate covered with an ultrathin AlN layer has demonstrated N-polarity. The dislocation density of such-grown InN layer has been significantly reduced (one order of magnitude lower than the conventional InN epilayers). The results have demonstrated great potential for improving the crystalline quality of hetero-epitaxial InN films. This concept can be easily adopted for other substrates.