Evaluation of strain and In content in (InGaN/GaN) multiquantum wells by x-ray analysis

A comprehensive x-ray analysis including Θ–2Θ scans, reciprocal space mapping, and x-ray reflectivity of $\text{10×(}\mathrm{InGaN/GaN})$ multiple quantum wells (MQWs) is presented. The layers were grown by low-pressure metal–organic chemical-vapor deposition. The strain state and the In concentration in (InGaN/GaN) MQW systems are evaluated with the help of reciprocal space maps around the symmetric (0002) and asymmetric $\text{(101̄5)}$ Bragg reflections. Depending on the In incorporation, the MQW system is fully strained, partially relaxed, or exhibits phase decomposition effects. The room-temperature photoluminescence emission energy of a fully strained $\text{10×(}{\mathrm{In}}_{\mathrm{0.125}}{\mathrm{Ga}}_{\mathrm{0.875}}\mathrm{N/GaN})$ MQW sample is 2.792 eV, which is 133 meV less than the calculated energy gap of 2.925 eV.