High reflectivity ultraviolet distributed Bragg reflector based on AlGaN/AlGaN multilayer

AlGaN/AlGaN distributed Bragg reflectors (DBRs) designed for the ultraviolet spectral region have been attained. The crack-free structures were grown on c-plane sapphire by plasma assisted molecular beam epitaxy (NOE). To minimize the built-in strain in DBRs, a thin buffer layer was used directly on e-plane sapphire. A peak reflectivity of 95% at 381 nm with a 21 run stop band width was obtained at room temperature (RT) using a 32.5 pairs Al0.7Ga0.3N/Al0.15Ga0.85N DBR. With a driving force for DBRs and emitting regions in wide band gap semiconductor microcavities, such as those based on GaN and ZnO, is the quest for cavity polariton which is the coupled mode between the exciton and photon modes. Moreover, the exploitation of cavity polaritons could be expected in the course of the development of extremely low-threshold optoelectronics devices.