Effect of AlGaN quantum barrier thickness on electron-hole overlapping in deep-ultraviolet laser diode

Abstract

AlGaN deep ultraviolet (DUV) with the high induced polarization emitters effect degrades the performance of the laser diode (LD) and brings a higher injection current density, resulting in reduced laser gain. Quantum barriers (QB) play a vital role in carrier flow (electrons, holes) in multiple quantum well (MQW). This work investigates the quantum barrier thickness effect on the performance of DUV LDs. Furthermore, the performance of DUV LD is enhanced by working on overlapping electrons and holes in the active region. The theoretically analyzed results illustrate that by minimizing the thickness of the AlGaN quantum barrier (QB), the electron-hole overlapping can be improved. Higher overlapping increases the rate of stimulated recombination. Compared with the reference structure AlGaN QB with 3 nm thickness, the emitted power can be increased by 11%, the optical confinement factor (OCF) by 71%, the electron-hole overlapping by 55%, and the laser gain by 149%. But selecting 12 nm QBs, power starts decreasing along with OCF, electron-hole overlapping, and laser gain. When the AlGaN QB is thicker, the height of the conduction band barrier diminishes, which boosts electron leakage coming from MQM, and when the valance band barrier's height is elevated, which reduces the efficiency of hole injection toward the MQW. Thus, it is concluded the below 12 nm QB thickness, the thinner the quantum barriers, the more carrier flows toward MQW, improving performance.