Influence of GaN Barrier Thickness on Optical Properties of In-Graded InGaN/GaN Multiple Quantum Wells

The barrier thickness dependences of the optical properties of In-graded InGaN/GaN quantum wells (QWs) are studied by photoluminescence measurement and theoretical calculation. The internal quantum efficiencies (IQEs) of the In-graded QWs with 8 and 16 nm barrier thicknesses and the conventional QWs with 16 nm barrier thickness are 35.0, 31.2, and 22.8% at 300 K, respectively. Besides, the In-graded QWs with 8 nm barrier thickness obtain the shortest radiative lifetime at 10–300 K. Calculation results demonstrate that combining the In-graded QWs with thinner barriers effectively increases the IQE by reducing the polarization field of the InGaN/GaN QWs.