Study On Emission Polarization Properties And Regulation In AlGaN-based Quantum Wells

In order to realize the structure design of high-performance AlGaN deep UV light-emitting diode,reduce the electron leakage,improve the hole injection,optimize the distribution of carrier,and improve the efficiency of positive light extraction.This article focuses on the problem of light emission characteristics that must be solved for deep UV LEDs.By optimizing the design of AlGaN light-emitting diodes to improve device performance,the specific research work is as follows:1.In this study,the effect of Al-composition modulation of the QWs including step-like and graded has been investigated and compared by APSYS software.The simulation results show that compared to the conventional and step-like AlGaN MQWs structures,the LOP and efficiency droop with the Al-composition graded wells are remarkably improved.The key factor in performance improvement is to achieve better modulation of the carrier distribution in the quantum wells while increasing the overlap between electron and hole wavefunctions,which contributing to more efficient recombination of electrons and holes,and thereby a significant increase in the LOP.2.In this study,design adopting step-like thick last quantum barrier(LQB)for DUV-LEDs has been investigated.Compared with the conventional LQB and thick LQB,the simulation results show that step-like thick last quantum barrier can significantly improve the internal quantum efficiency and light-emitting power of the device.The key factor in performance improvement is that the step-like thick LQB is prove to increase the effective potential heights for electrons of AlGaN EBL,and thus enhances the electron confinement in the active region.Thereby reduce the electron leakage current and increase the hole injection efficiency via this novel LQB,therefore improving the IQE as well as the LOP.3.In this study,the effect of asymmetric step LQB structure for DUV-LEDs has been designed and simulated by APSYS software.The conventional LQB and thick LQB used as a reference for this study.The simulations results show that the asymmetric step LQB can effectively enhances the electron confinement in the active region,and increase the injection and transmission efficiency of holes.In-depth analysis shows that when the thickness of the step layer with a higher composition is smaller,the smaller average electric field in QWs can increase the overlap between electron and hole wave functions,achieve more efficient recombination,thereby significantly improving the optoelectronic performance of the device.