Correlation of Optical, Structural, and Compositional Properties with V-Pit Distribution in InGaN/GaN Multiquantum Wells.

InGaN/GaN double heterostructures and multiquantum wells (MQWs) have been successfully developed since more than 20 years for LED lightning applications. Recent developments show that state-of-the-art LEDs benefit from artificially generated V-pit defects. However, the control of structural and chemical properties plays a tremendous role. In this paper, we report on the lateral distribution of V-pit defects and photoluminescence of InGaN/GaN MQWs grown on thick GaN on patterned sapphire substrates. The synchrotron-based scanning X-ray diffraction microscopy technique K-map was employed to locally correlate these properties with the local tilt, strain, and composition of the InGaN/GaN MQW. Compositional fluctuation is the main factor for the variation of photoluminescence intensity and broadening. In turn, V-pit defects align along small-angle grain boundaries and their strain fields are identified as a reason for promoting the InGaN segregation process on a microscale.

Structural and optoelectronic characterization of RF sputtered ZnSnN(2).

ZnSnN(2), a new earth-abundant semiconductor, is synthesized and characterized for use as a photovoltaic absorber material. Results confirm the predicted orthorhombic Pna2(1) crystal structure in RF sputtered thin films. Additionally, optical measurements reveal a direct bandgap of about 2 eV, which is larger than our calculated bandgap of 1.42 eV due to the Burstein-Moss effect.