A simple method to overcome the limitation of hybrid monochromator in the identification of peaks in the HRXRD pattern of Al0.4Ga0.6N/Al0.6Ga0.4N multi quantum wells

Abstract

Features related to AlN buffer layer, thick AlGaN bottom layer, and AlGaN quantum well structure are identified by performing High resolution X-ray diffraction (HRXRD) measurements on Al0.4Ga0.6N/Al0.6Ga0.4N multi quantum well sample. HRXRD measurements reveal an anomalous peak which is not predicted by the simulations using Takagi-Taupin equations based on the dynamical theory of X-ray diffraction. However, the peak doesn’t appear when the diffraction pattern is recorded using the HRXRD beam line of Indus-2 Synchrotron radiation source. Systematic investigations reveal that the anomalous peak is related to some unknown scattering originating from the X-ray optics used in the hybrid monochromator of commercial HRXRD system. It limits the usefulness of HRXRD technique for the investigation of AlGaN/AlGaN MQW samples. In view of this, a simple method for the elimination of anomalous peak from the HRXRD pattern is also demonstrated. In literature, similar anomalous peaks are often associated with the incorporation of metallic clusters, impurities, and additional crystallographic phases in epilayer. A word of caution is therefore necessary that the origin of anomalous peak in HRXRD pattern should be first confirmed before assigning the same to a particular physical phenomenon.