A GaN-based vertical-cavity surface emitting laser (VCSEL) structure featuring a silicon-diffusion-defined current blocking layer for lateral confinement is described. Sub-milliamp threshold currents were achieved for both 3- and 5-μm-aperture VCSELs under continuous-wave operation at room temperature. The vertical cavity was defined by a top dielectric distributed Bragg reflector (DBR) and a bottom epitaxial DBR. The emission spectrum exhibited a single peak at 411.2 nm with a linewidth of 0.4 nm and a side mode suppression ratio of more than 10 dB before device packaging. The full-width-at-half-maximum divergence angle of the 3-μm-aperture VCSEL was as small as approximately 5° which is the lowest number reported. These results implied the 3-μm-aperture VCSEL was in near single-mode operation.
For GaN-based vertical-cavity surface-emitting lasers (VCSELs), a suitable current confinement layer is essential for high-performance devices. The effect of different current confinement layers, including SiO2, AlN, and diamond, on the performance of GaN-based VCSELs was compared through simulation. The devices’ heat dissipation and current confinement characteristics were analyzed based on the electro-opto-thermal model. Considering thermal management, the diamond was a better candidate under high injected current. Benefiting from the excellent heat dissipation, the device with diamond shows a significant improvement in output power and the thermal roll-over current. This work gives a superior option for the current confinement layer and can be helpful for future design and fabrication of high-power GaN-based VCSELs.
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