Cascade nitride VCSEL designs with tunnel junctions

The performance of various possible designs of 400-nm nitride vertical-cavity surface-emitting lasers (VCSELs) has been analyzed with the aid of an advanced three-dimensional (3D) thermal-electrical-optical-gain self-consistent threshold simulation. It has been demonstrated that it is practically impossible to reach fundamental-mode operation in nitride VCSELs of the traditional design with two ring contacts. To enhance this desired operation, the uniformity of current injection into VCSEL active regions should be dramatically improved. Therefore, we have focused our research on designs with tunnel junctions and/or a semitransparent contact. In particular, it has been proved that a design with two cascading active regions, two tunnel junctions and a semitransparent contact may offer the most promising room-temperature performance characteristics for both pulse and continuous-wave operations. In particular, this design offers high mode selectivity with a distinct fundamental transverse mode domination. The simulations also reveal that the thickness and localization of the semitransparent contact, as well as the localization of active regions and tunnel junctions, are crucial for successful construction design. PACS 42.55.Px; 85.30.De; 85.60.Jb