Fabrication of crack-free AlN film on sapphire by hydride vapor phase epitaxy using an in situ etching method

Crack-free AlN films were grown on sapphire by hydride vapor phase epitaxy, with in situ etching applied during growth. Nanoscale voids were formed at a chosen growth stage by interrupting the growth and performing in situ etching in an H2 atmosphere at elevated temperature. Transmission electron microscopy showed the voids located at strongly distorted locations, and hence relaxing the strain and reducing the dislocation density. Raman spectra and X-ray diffraction measurements further demonstrated important role played by the nanoscale voids in releasing misfit strain and reducing dislocations. This work opens a promising perspective for fabricating thick, high-quality AlN.