Dependence of green InGaN/GaN multiple quantum well luminescence properties on the well width

The c-plane InGaN/GaN multiple quantum well (MQW) heterostructures act as the core active region for visible light-emitting diodes (LEDs). Well thickness modulates behaviors such as quantum confined Stark effect, strain status, and carrier localization simultaneously. To investigate the well thickness dependent material and luminescence properties, a series of InGaN/GaN MQW samples with varied well widths were fabricated. X-ray diffraction and reciprocal space mapping verify pseudomorphic growth without macroscopic lattice relaxation for all samples. Comprehensive characterizations including electroluminescence, temperature-dependent photoluminescence, cathodoluminescence, and microphotoluminescence were carried out. The results reveal that increased well thickness aggravates microscopic strain inhomogeneity even in the absence of global lattice relaxation. Thicker wells induce severe alloy disorder, larger carrier-localization parameter, higher density of nonradiative recombination centers, as well as degraded luminescence efficiency and aggravated thermal effects under electrical injection. This work demonstrates that excessive well thickness should be avoided for InGaN/GaN MQW active regions, even when the well geometry still belongs to the thin-well window. It provides experimental references for the optimization of practical InGaN/GaN MQW LED designs.