UV laser diodes have many advantages over existing gas lasers and solid-state lasers, such as compact size, high efficiency, low power consumption, controllable wavelength, and no use of rare noble gases, and are therefore attracting much attention for their practical application. In this presentation, we introduce our AlGaN-based laser diode in the UV-B region (wavelength of 280~315 nm), which has been difficult to realize in the past. Two bottlenecks existed in the realization of this device: the difficulty of realizing a layer structure that simultaneously realizes the formation of a favorable optical cavity and the high carrier density injection required for laser oscillation, and the difficulty of obtaining high-quality AlGaN crystals with low carrier injection that provide a large optical gain. Our group has solved these problems by using a structure with polarized doping in the p-cladding layer and a high-quality lattice-relaxed AlGaN template, and demonstrated laser oscillation by current injection. I would like to discuss the details of these breakthroughs. I would also like to introduce the latest device performance.
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