Inhomogeneous Current Injection and Filamentary Lasing of Semipolar (2021¯) Blue GaN‐Based Vertical‐Cavity Surface‐Emitting Lasers with Buried Tunnel Junctions

Blue semipolar vertical‐cavity surface‐emitting lasers with a buried tunnel junction current aperture are demonstrated under continuous‐wave operation with a differential efficiency of 4% and a threshold current of 2.7 mA for a lasing mode at 452 nm. The effects of the aperture diameter on these 9λ cavity length devices are presented, showing that the differential efficiency increases with aperture size, whereas the threshold current density remains constant for apertures larger than 10 μm. Filamentary lasing is observed in the larger aperture sizes, and it is suggested that this mode behavior is due to current injection inhomogeneity across the aperture. This theory is supported by the correlation between optical nearfield images and thermal microscopy images.