Structural and optical properties of GaN/AlGaN multiquantum wells with an AlGaN insertion monolayer in the GaN well

We have studied the influence of an AlGaN insertion layer in a GaN quantum well on the light emission from a strained GaN/AlGaN multiple-quantum well system. The structural properties of GaN/AlGaN multiquantum wells of the same composition were studied by using the reciprocal space mapping and simulation techniques of high-resolution x-ray diffraction. The lattice constants along the in-plane direction determined from the (105) reciprocal space maps were a = 3.161 angstrom for normal multiquantum wells and a = 3.152 angstrom for interlayer multiquantum wells. The spatial localization of the quantum well emission was unambiguously determined by monochromatic cathodoluminescence measurements. This observation indicates that the blue emission near 2.96 eV in the interlayer multiquantum wells originates from the MQW region, rather than from a deep level in the GaN buffer layer. These transitions could be a quantum confined Stark effect due to the piezoelectric field caused by the strain between the well and barrier.