On-wafer fabrication of etched-mirror UV-C laser diodes with the ALD-deposited DBR
Tadayoshi Sakai, Maki Kushimoto, Ziyi Zhang, Naoharu Sugiyama, L. J. Schowalter, Yoshio Honda, Chiaki Sasaoka, Hiroshi Amano
Abstract
We have demonstrated an on-wafer fabrication process for AlGaN-based UV-C laser diodes (LDs) with etched mirrors and have achieved lasing for 100 ns pulsed current injection at room temperature. A combined process of dry and wet etching was employed to achieve smooth and vertical AlGaN (11¯00) facets. These etched facets were then uniformly coated with a distributed Bragg reflector by atomic layer deposition. A remarkable reduction of the lasing threshold current density to 19.6 kA/cm2 was obtained owing to the high reflectivity of the etched and coated mirror facets. The entire laser diode fabrication process was carried out on a whole 2-in. wafer. We propose this mirror fabrication process as a viable low-cost AlGaN-based UV-C LD production method that is also compatible with highly integrated optoelectronics based on AlN substrates.