Technological feasibility of III-nitride vertical cavity surface emitting laser (VCSEL) has been hindered by the lack of an electrically conductive, easily manufacturable, wide reflection stop band distributed Bragg reflector (DBR). Here, we present the first electrically injected III-nitride VCSEL on an electrically conductive DBR using nanoporous (NP) GaN. The measured threshold current density and the maximum light output power were 42 kA/cm2 and 0.17 mW, respectively, at 434 nm. Vertical injection was demonstrated and showed no deterioration in the threshold current density or slope efficiency, demonstrating the feasibility of vertical injection in NP GaN VCSELs. Filamentary lasing was observed, and its effect on the slope efficiency and the lasing linewidth is studied. Initial measurements showing the correlation between the measured high threshold current density and surface undulations are presented and discussed.
The research at Yale was partially supported by the IP Group, Inc. The authors acknowledge the use of Yale University Cleanroom, a core facility supported by the Provost Office. The authors would like to thank Dr. Y. Sun, Dr. S. Rinehart, and Mr. K. Woods for the useful cleanroom discussions and fabrication assistance; Dr. L. Frunzio for help in pulsed measurements; and Dr. C. Zhang and Mr. C. Mi for the useful discussions and assistance. The work at SCNU was supported by the NRF of Korea (No. NRF-2014R1A6A1030419).