Research On The Electrode Structure Design Of Nitride-based Ultraviolet LED

III-V nitride semiconductors have been deeply studied in high-brightness visible(light emitting diodes)LEDs because of their wide and direct bandgap.Nitride-based(ultraviolet)UV LED devices have been extensively studied in terms of material growth or structure design.While increasing their low internal quantum efficiency,improving the light extraction efficiency is also one of the difficulties worthy of attention.Single-layer transparent electrode structure is generally used as ultraviolet LED electrode currently.Although it can take into account of current conducting and light transmission at the same time,the phenomenon of current crowding is occurred under high injection current,which is not conducive to the stable operation of the ultraviolet LED under high current.Designing a new UVLED electrode structure that can be applied to high current working mode is the basis for manufacturing high-performance ultraviolet LED devices.Therefore,this article selects an appropriate UV LED basic structure,and then designs and studies several different new transparent electrode structures on this UV LED basis.Firstly,the basic structure of the UV LED required for the experiment was selected and optimized.Patterned sapphire substrate was used to reduce the dislocations formed during the growth process and improve the crystal quality of the epitaxial layer.The APSYS simulation research results show that superlattice electron barrier layer can effectively inject holes while reducing electron leakage,improve the droop effect of the LED and provide a good basis for subsequent electrode experimental research.The COMSOL simulation software was used to simulate the(indium tin oxide)ITO/Au/ITO electrode structure,and it was found that the addition of the Au interlayer plays a positive role in optimizing the spreading of the current and provided ideas for the subsequent experiment.Secondly,the experimental study of the above-mentioned simulated structure was carried out and the optimized wavelength of 370 nm ultraviolet LED structure was used.The electron beam evaporation equipment was used to fabricate two ITO layers.The results of the experiment show that inserting Au layer effectively improve the ultraviolet performance of LED.Compared with UV LED devices without Au interlayer,the(light output power)LOP of transparent electrode structure devices with 1,5,and 10 nm Au interlayer has increased by 65.0%,26.6% and 60.8% at 350 m A.The light distribution test shows that the luminescence distribution of the UV LED device containing the Au interlayer transparent electrode structure is more extensive and uniform.The relationship between the surface morphology of the device with 10 nm Au interlayer and its high luminous intensity is also explained.Finally,the transparent electrode structure of different metal interlayer was studied.The results of UV LEDs with transparent electrode structures of ITO/Au/ITO,ITO/Ni/ITO,ITO/Sc/ITO fabricated by magnetron sputtering show that the ITO/Ni/ITO structure has the most significant effect on light output performance.And at a working current of 350 m A,for the ITO/Au/ITO transparent electrode structure,the device with a 1 nm metal interlayer has better optoelectronic properties;for the ITO/Ni/ITO transparent electrode structure,the device with a 10 nm metal interlayer has better optoelectronic properties;for the ITO/Sc/ITO transparent electrode structure,the device with a 5 nm metal interlayer has better optoelectronic properties;this is due to the compromise between the light absorption characteristics and the conductivity characteristics of the interlayer metal.