Control of optical loss in GaN-based planar cavities

Optical losses in GaN-based resonant planar cavity are discussed and experimentally examined in respects of indium tin oxide (ITO) inner-cavity current spreading layer, the defect-rich GaN layer, and multi-quantum well (MQW) active region. Devices with different structures are adopted to study the optical loss. It is demonstrated that a thin ITO layer and a coupled MQW active region are essential to achieve a low loss and high Q-value cavity. The results show that low-loss MQW design is particularly important in fabricating high-Q value GaN-based planar cavities.