Performance of Ultraviolet‐B Laser Diodes on AlGaN Templates Prepared using Different Fabrication Methods

Herein, the differences in the characteristics of ultraviolet-B (UV-B) laser diodes (LDs) are investigated and fabricated on AlGaN templates prepared using two types of fabrication methods: 1) spontaneous nucleation in which AlGaN is grown 3D from spontaneously generated AlN crystal nuclei and 2) AlN nanopillar in which AlGaN is grown on AlN nanopillars. The LD formed on the AlGaN fabricated using the AlN nanopillar method of slope efficiency and maximum peak light output power is improved four and six times, respectively, which are significantly better compared with the spontaneous nucleation method. The analysis also confirms the differences in injection efficiency and internal loss in the semiconductor crystal. Furthermore, detailed analysis of the current-voltage characteristics shows that the AlN nanopillar method has lower reverse leakage current and n-value than the spontaneous nucleation method. Comparison of these differences with crystallographic properties suggests that these differences in device properties are manifested by differences in V-shaped pits and dislocation density. The reduction of dislocations and V-shaped pit density in an AlGaN template is important to realize high-performance UV-B LDs, and the AlN nanopillar method is found to be useful for the fabrication of a suitable AlGaN template.