Optical polarization and internal quantum efficiency for InGaN quantum wells on a-plane GaN

Non-polar a-plane (1 1 –2 0) InGaN/GaN multiple quantum wells have been grown by metal-organic chemical vapor deposition on r-plane sapphire substrates. An optical polarization analysis was performed using edge-emitting and surface-emitting photoluminescence measurements. Non-polar a-plane MQWs show a lower transverse electric/transverse magnetic polarization ratio because of the reduced piezoelectric field in the growth direction. A strong polarization was observed in the surface-emitting spectrum for a-plane MQWs. The anisotropic polarization has an angle of 120° between the maximum and minimum components for the a-plane InGaN/GaN MQWs. In addition, this analysis revealed a lateral localized confinement in a-plane InGaN/GaN MQWs due to anisotropic growth along the GaN (1 –1 0 0) and (1 1 –2 0) directions. The internal quantum efficiency of a-plane and c-plane InGaN/GaN MQWs was obtained in the temperature- and power-dependent surface-emitting PL spectra.