Recent development of UV-B laser diodes

This review paper describes the historical development, current issues, and future expectations of UV-B laser diodes, which are expected to be adopted in various applications such as in microfabrication and biotechnology in the near future. To achieve RT operation of UV-B laser diodes, several challenges need to be addressed, including the development of a crystal growth technique for high-crystalline-quality AlGaN films that enables laser oscillation with a low excitation carrier density, and the development of a semiconductor layer structure for simultaneous formation of a desirable optical cavity and injection of high-density carriers (operation of high current density), allowing laser oscillation in the active layer. These challenges and the corresponding technologies that have overcome them are reviewed. The current status of device characteristics and future challenges are also discussed.