Effects of the Stepped-Doped Lower Waveguide and a Doped p-Cladding Layer on AlGaN-Based Deep-Ultraviolet Laser Diodes

The performance of deep ultraviolet (DUV) laser diodes (LDs) may be affected by structural variations in the composition of AlGaN devices. In this work, we investigate the impact of structural variations in three AlGaN-based DUV-LDs, namely, the traditional DUV-LD (D1), traditional device structure with stepped-doped lower waveguide (LWG) (D2), and Mg-doped p-cladded D2 (D3). In this study, we closely analyze the performance dependence of different structural variations on the traditional DUV-LD. The stepped-doped LWG method utilized in D2 has proven to be an improvement factor among the three DUV-LDs. Moreover, the threshold current decreases when the LWG doping concentration increases. An adequately constructed stepped-doped LWG layer replaces the homogeneously and heavily doped LWG layer in D1, which decreases the electron leakage current and increases the hole injection current. The performance gains of AlGaN-based ultraviolet laser diodes are demonstrated using the simulation software LASTIP. The deep wavelength of all the DUV-LDs is 269 - 280 nm, with D1, D2, and D3 exhibiting an operating threshold voltage of 2.64, 4.24, and 4.24 V, respectively, and a lasing threshold current of 0.4, 0.002, and 0.002 A, respectively. Overall, D2 is considered as the preferred LD, because it achieves the best reduction in total optical loss, thereby resulting in 40% optical confinement.