m-Plane GaN Split-Well Direct-phonon Terahertz Quantum Cascade Laser

In this work, we have theoretically investigated GaN-based terahertz quantum cascade laser (THz QCL) structure, modeled for growth along the non-polar m-plane. The design employs the split-well direct-phonon (SWDP) scheme and is analyzed using the Non-equilibrium Green’s Function (NEGF) approach. The proposed design successfully addresses key limitations identified in previous studies, particularly the challenge of balancing high gain with lower current density thereby mitigating the risk of thermal damage. By introducing a thin barrier within the wider well, we achieved a substantial reduction in doping density leading to lower current density while preserving strong gain performance. Our simulations show that the m-plane SWDP GaN-based QCL can achieve lasing at ~ 8.7 THz, with 14% Al in the barrier and 7% Al in the intra-well barrier, with maximum operating temperature (Tmax) up to ~ 280 K. This lasing frequency exceeds the typical limits of GaAs-based THz QCLs, demonstrating the potential of GaN-based designs for extended frequency coverage and high-temperature operation.