Evolution of indium segregation in metal-polar In0.17Al0.83N lattice-matched to GaN grown by plasma assisted molecular beam epitaxy

The impact of growth conditions on indium segregation in metal-polar In0.17Al0.83N lattice-matched to GaN grown by plasma assisted molecular beam epitaxy is reported. A series of lattice-matched InAlN films was systematically grown over a wide range of temperatures and active nitrogen fluxes. The growth conditions include those reported in the literature as conducive to homogeneous In0.17Al0.83N (Kaun et al., 2014). However, honeycomb indium composition modulation was found in all InAlN films. For samples grown at the highest temperature and nitrogen flux, InAlN layers exhibit larger and more irregular cells with emergence of open cell boundaries. We conclude that the studied growth conditions alone are not sufficient to eliminate the 'honeycomb' structure in metal-polar InAlN lattice-matched to GaN, and that the physical process necessary for reproducible growth of homogeneous In0.17Al0.83N requires further clarification.