Characterization of InGaN thin films using high-resolution x-ray diffraction

Wurtzite InGaN thin films grown by metalorganic chemical vapor deposition on sapphire substrates with and without GaN buffer layers are investigated by high-resolution x-ray diffraction measurements. The structural quality, lattice constants, strain, and indium composition of 100 nm thick films with In concentrations up to 33% are evaluated by measuring symmetric (00.2) and asymmetric (20.5) reflexes. The quality of the InGaN layers with widely different biaxial stress is measured and compared. An analytical solution for the determination of the In content of strained epitaxial layers is introduced. The results show that neglecting the strain can result in a severe miscalculation of the In concentration.