Simulation of performance enhancement of GaN-based VCSELs by composition gradient InGaN last-quantum barrier

Abstract Electron leakage in the active region decreases the internal quantum efficiency and impedes the performance of gallium nitride (GaN)-based vertical-cavity surface-emitting lasers (VCSELs). In this study, we propose a novel InGaN last-quantum barrier (LQB) structure with gradient indium (In) composition, and the device performance was simulated by the commercial software PICS3D. Compared with the device with conventional GaN LQB, the electron leakage is greatly reduced and the hole injection efficiency is also improved by the graded LQB structure. Consequently, the threshold current is reduced by 44%, and output power is increased by 392% in GaN-based VCSEL based on composition gradient InGaN LQB. The composition gradient InGaN can also allow us to increase the thickness of the LQB in epitaxy without degrading the carrier injection efficiency due to the reduced polarization in the LQB. The results of this study suggest that the composition gradient InGaN LQB is promising for the realization of high-performance GaN-based VCSELs.