Well-width dependence of photoluminescence emission from a-plane GaN/AlGaN multiple quantum wells

This work investigates the room-temperature photoluminescence (PL) characteristics of nonpolar $\mathrm{GaN}\text{/(∼100\hspace{0.5em}}{\mathrm{\AA Al}}_{\text{0.16}}{\mathrm{Ga}}_{\text{0.84}}\mathrm{N})$ multiple quantum wells (MQWs) in comparison to c-plane structures as a function of GaN quantum well width. 10-period a-plane and c-plane MQW structures were simultaneously regrown on the appropriate GaN/sapphire template layers via metalorganic chemical vapor deposition with well widths ranging from 20 to 70 Å. The PL emission energy from a-plane MQWs followed a square well trend modeled using self-consistent Poisson–Schrödinger calculations while the c-plane MQW emission showed a significant redshift with increasing well width which is attributed to the quantum-confined Stark effect. Despite a higher dislocation density, the a-plane MQWs exhibit enhanced recombination efficiency as compared to the c-plane wells since well emission is no longer observed for c-plane wells wider than 50 Å. Optimal PL emission intensity was obtained for 52 Å a-plane wells compared to 28 Å c-plane wells, revealing the effects of internal fields on quantum well emission.