Tunnel junction for long-wavelength vertical-cavity surface-emitting lasers

To improve the performance of long-wavelength vertical-cavity surface-emitting lasers (VCSELs), we performed an extensive study of tunnel junctions for current injection and confinement. The introduction of a tunnel junction in long-wavelength VCSELs can substantially improve the current injection scheme, because an n-type material is utilized in the p-side region by inserting a tunnel junction. We fabricated long-wavelength lasers with a tunnel junction formed by metalorganic chemical vapor deposition (MOCVD) using tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs), and confirmed the current homogenization effect. We also proposed and fabricated a current confinement structure by means of a simple fabrication process using a tunnel junction, i.e., the automatically formed tunneling aperture (AFTA). The AFTA, has a tunnel junction aperture and can be formed automatically during electrode thermal annealing. We investigated the formation condition of the AFTA by varying the annealing temperature and time. We performed secondary ion mass spectroscopy (SIMS) and tunneling electron microscopy (TEM) of an annealed tunnel junction in order to understand the formation of AFTA.