Effect of the changing DBR doping concentration on Performance of MQW GaN-based Vertical Cavity Surface Emitting Lasers

This study is an attempt to investigate the effect of distributed Bragg reflectors (DBRs) doping concentration on the GaN-based vertical cavity surface emitting lasers (VCSEL) using Integrated System Engineering Technical Computer Aided Design ( ISE TCAD ) software. Uniformly n (Up) and p (Down) doping concentration, changed ranging from 5e+17 to 1e+19 cm-3. The observation revealed that as DBR doping concentrations rose, the output power increased and the threshold current reduced. These are attributed to the increase in radiative recombination and decrease in the optical losses which has induced from the scattering process. The threshold current reaches minimum value at DBR doping concentration of 5e+18 cm-3 which is the optimal value for the doping concentration. Two designs of VCSEL were proposed to enhance the performance of VCSEL. The first design including 8 DBRs layers close to the active region were doped with concentration of 5e+18 cm-3 and the rest of DBRs were doped with concentration of 1e+19 cm-3. The active region and cladding layers were undoped. The second design is similar to the previous design except that the cladding layers also were doped with concentration of 5e+18 cm-3. The results revealed that the first design had high enhancement of the laser performance due to the wide active region compared with the second design. Finally, the comparison of the effect of uniform and non-uniform DBR doping concentration on the VCSEL performance was included