Optical polarization characteristics of m ‐plane InGaN films coherently grown on ZnO substrates

We investigated the optical polarization characteristics in m ‐plane In 0.33 Ga 0.67 N films grown on ZnO substrates using room temperature grown epitaxial GaN buffer layers. We found that m ‐plane InGaN films with a film thickness of 400 nm can be grown coherently on m ‐plane ZnO substrates at 660 °C by pulsed laser deposition. Reciprocal space mapping revealed that the InGaN film possesses compressive strains as large as 1.7% and 2.6% along the a ‐ and c ‐axes, respectively. Photoluminescence polarized along the c ‐axis with a peak wavelength of 505 nm was observed from the strongly compressed InGaN film. We also found that the degree of polarization depends strongly upon the strain in the m ‐plane InGaN, and the coherent growth of m ‐plane InGaN on ZnO substrates leads to an enhancement in c ‐axis polarization. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)