Epitaxial Material Growth And Device Research Of High Efficiency 850nm Infrared LED

The infrared light emitting diode technology and performance indicators of security monitoring have high requirements,because security monitoring covers a wide range,long distance and long monitoring time,and the LED chip works at constant current for a long time,which requires high LED photoelectric conversion efficiency,reliable service life and excellent performance.Therefore,how to greatly improve the luminous efficiency of infrared LED is a technical challenge faced by the industry.This paper mainly studies the growth of epitaxial materials and devices for monitoring common high-efficiency 850 nm infrared light-emitting diodes.There are two ways to improve the luminous efficiency of infrared LED: one is to improve the internal quantum efficiency.The low internal quantum efficiency is mainly due to the internal defects in the material and the internal loss caused by carrier leakage;The second is to improve the light extraction efficiency.The most effective scheme is to adopt the reverse polarity chip process,and add antireflection film,ODR mirror and surface roughening technology to improve the light extraction efficiency.In this paper,metal organic chemical vapor deposition(MOCVD)method is used for epitaxial material growth,which is deeply discussed from the aspects of epitaxial material selection,growth process and material photoelectric performance analysis.The growth conditions and epitaxial structure of semiconductor materials are optimized to improve the crystal quality of epitaxial materials,reduce the internal defects of materials and greatly improve the internal quantum efficiency of infrared light-emitting diodes.The adjustment method for epitaxial structure is as follows:1)Optimize the long crystal quality of AlGaAs limiting layer.The higher the Al component of AlGaAs,the wider the band gap and the stronger the restriction on carriers,but the high Al component is easy to absorb impurities and cause non radiative recombination centers.Through the experiment,the Al component of the limiting layer is adjusted to 45%,and the radiation power is significantly improved.2)Optimize the crystal quality of AlGaAs current spreading layer.The in adhesion brought by Ga In P material is reduced by reducing the growth rate of AlGaAs.The current spreading layer adopts step growth rate,which grows slowly at the initial stage and gradually increases the speed to reduce defects,dislocations and defects.Through the experiment,the current spreading layer is divided into three gradients: 0.1nm/s,0.4nm/s and 1.6nm/s,which can effectively improve the internal quantum efficiency.3)The FWHM is reduced by adjusting the thickness of the quantum well.The light-emitting process of infrared light-emitting diode is to apply current at both ends of the diode,and electrons and holes recombine in the quantum well.High-energy electrons may be at different energy levels,and they will spontaneously radiate to different low-energy levels,so the emitted photon energy is different and the wavelength is different.In order to reduce the FWHM,we need to reduce the number of energy levels in the radiation process.In this study,the FWHM is improved by adjusting the thickness of quantum wells.The FWHM can be reduced by 4.3 nm by thickening the quantum well to 6 nm.