Optically pumped VCSELs with a 1λ thick optical cavity lasing at 375 nm have been demonstrated using a pulsed 248 nm KrF excimer laser source. To realize a high-reflectivity mirror on the bottom of the cavity, five-period airgap/ Al0.05Ga0.95N DBRs with a large refractive index contrast have been employed while the top mirror was formed by dielectric DBRs consisting of twelve pairs HfO2/SiO2. The lowest threshold incident power density measured at room temperature was estimated to be ~270 kW/cm2. The achieved optically pumped VCSEL demonstrates the possibility that the airgap/AlxGa1-xN DBRs can be used as a mirror for injection laser devices.
We report III-N surface-emitting resonant-cavity light-emitting diodes (RCLEDs) at λ = 375 nm using a novel hybridmirror approach. The hybrid mirrors consist of 5 pairs of air-gap/AlGaN distributed Bragg reflector (DBR) at the bottom side of the vertical cavity and HfO<sub>2</sub>/SiO<sub>2</sub> dielectric DBR (DDBR) on the top to facilitate the formation of a resonant cavity for nitride-based surface light emitting diodes. The air-gap/AlGaN DBR replaces the conventional thick stack of semiconductor DBR to achieve high reflectivity. Hybrid-mirror III-N RCLEDs with airgap/AlGaN DBR mirror were fabricated and the results showed that the III-N RCLEDs achieved high current density operation up to 40 kA/cm<sup>2</sup> with a peak emission wavelength atλ = 375 nm and a full-width-half-maximum (FWHM) of 9.3 nm at room temperature.