Simulation Study On Luminous Efficiency Improvement And Optimization Of Blue-Violet LED

Due to the huge demand for high-density digital storage,lighting and environmental protection,the study of GaN-based light-emitting diodes(LEDs)has become a research hotspot,especially in terms of the luminous efficiency of short-wavelength LEDs under high current injection.This paper focuses on the improvement and optimisation of the luminous efficiency of violet and blue LEDs.Firstly,the research background and development status of violet and blue LEDs,the nature and structure of group Ⅲ nitride materials,the operating principles and physical properties of LED devices are outlined.Finally,the Al GaN/GaN violet LED and InGaN/GaN blue LED devices are simulated under different temperatures,polarisations and stresses using the APSYS software,and the luminous efficiency of the blue/violet LEDs is investigated.1.The effect of temperature on the optical and electrical characteristics of Al GaN/GaN violet LEDs and InGaN/GaN blue LED devices was investigated.The results show that for the violet LEDs,the peak luminous wavelengths are 355.3 nm,356.9 nm,358.0 nm and 359.1 nm when the temperatures are 255 K,295 K,335 K and 375 K,respectively;the light output power is 14.8 m W,12.2 m W,9.9 m W and 8.6 m W,respectively,which is reduced by 50.52 %;Efficiency-Droop Factor decreased by 37.56 % from 37.65 % to 0.09 %.For the blue LEDs,the corresponding peak wavelengths were 415.2 nm,419.0 nm,420.9 nm and 422.9 nm at the four temperatures;the light output power was 11.5 m W,8.6 m W,5.7 m W and 2.1 m W respectively,a decrease of 81.81 %;the Efficiency-Droop Factor decreased by The efficiency-droop factor decreased by 23.79 %,indicating that the improvement of the luminous efficiency of violet LEDs by temperature is more significant than that of blue LEDs,with better optimisation performance.2.The luminescence characteristics of Al GaN/GaN violet LEDs and InGaN/GaN blue LEDs with semi-polar m-plane and non-polar r-plane quantum well structures were analysed and compared with polar c-plane structures to investigate the influence of polarisation effects on the luminescence performance of blue/violet LED devices.The results show that for the violet LEDs,the light output power of the samples with semi-polar and non-polar multi-quantum well structures is increased by 132 % and 180 % compared to the polar structures when the current density is 300 A/m,and the peak spontaneous emission spectra are 4.99 times and 2.67 times higher than those of the polar structures,respectively.For blue LEDs,the light output power is increased by 285 % and 104 % for samples with semi-polar and non-polar structures compared to polar structures when the current is 300 A/m.The effect of non-polar structures on blue LEDs is not as great as for violet LEDs,with a corresponding reduction in the peak intensity of the spontaneous emission spectrum.In conclusion,the application of non-/semi-polar quantum well structures improves the polarisation effect in the luminescent active region of the LEDs by limiting electron leakage,increasing hole injection,and increasing the wave function overlap between electrons and holes,and its induced quantum confinement Stark effect caused by the built-in electric field,which in turn can enhance the radiation complex efficiency of the device and improve the Efficiency-Droop effect,improving and optimising the luminescence performance.The luminous performance of the device is improved and optimised.3.The effects of stress on the optical and electrical properties of Al GaN/GaN violet LEDs and InGaN/GaN blue LEDs were investigated.The results show that for the violet LED,the peak luminescence wavelength of the spontaneous emission spectrum is 359.7 nm at 0 GPa,and the peak luminescence wavelengths are 359.4 nm and 358.0 nm when the stress is 1 GPa and 2GPa,with a blue shift;when the current density is 600 A/m and the stress is 1 GPa and 2 GPa,the light output power decreases compared to 0 GPa by 15.89 % and 27.90 %,respectively,and the radiation complexation rate in the multi-quantum well structure was reduced by 15.75 %and 17.25 %,respectively.For blue LEDs,the peak wavelength is 414.8 nm when the stress is0 GPa and 414.6 nm and 414.2 nm when the stress is 1 GPa and 2 GPa,and the blue shift also occurs.The reduction in radiant complex rate was even more pronounced,by 11.93 % and28.50 %,respectively.Therefore,stress regulation has obvious advantages for improving the luminous efficiency of LED devices and can largely optimise the performance of LED devices.