Fabrication Of AlGaN-based UV LED With Metal-doped Oxide Transparent Electrodes

When AlN?aluminum nitride?is added into Ga N system,the emission wavelength of AlGaN-based LED can realize the full spectrum coverge of 400²10nm.It is widely used in curing,printing,disinfection and biometric identification.At present the photoconversion efficiency and output power of UV LED are still low,while the UV LED transparent electrodes has the absorption of ultraviolet light.The investigation of UV LED transparent electrode is of great significance to improve the optoelectronic performance.In the paper,we investigate the fabrication method of metal-doped transparent conductive thin films,and two kinds of transparent electrode films contacting with p-GaN surface are prepared.By doping Al and Ti into ITO thin films,the transmittance of the films in the ultraviolet band is improved and the sheet resistance of the films is reduced.The experimental results show that the transmittance of the films doped with Ti and Al can reach90.8%and 91.2%in 395nm and 365nm,respectively.The sheet resistance of ITO films is reduced from 45?/?to 38.9?/?.Metal-doped ITO films were used to prepare 395nm and365nm AlGaN-based UV LEDs,respectively.At the 120mA injection current,the voltage of the devices decreased by 0.5V and 0.3V,respectively,their optical output power increased by 19.7%and 14.7%,respectively,which is compared with that of the 80nm ITO films.A novel metal-doped Ga₂O₃ transparent conductive contact film is also studied.The Ni/Ga₂O₃/Ag/Ga₂O₃ multilayer thin film?Ni-M-Ga₂O₃?was grown by sputtering.The transmittance at 335nm wavelength reaches 85.6%.Compared with the 90nm ITO film,the sheet resistance is reduced by 28.5?/?,the resistivity is reduced by 81.7%,and the transmittance is increased by 1.48 times.Furthermore the ohmic contact characteristics between Ga₂O₃ film doped with Ni/Ag and surface p-GaN are analyzed.The optical output power of 365nm LED prepared by Ni-M-Ga₂O₃ film is 31.1%higher than that of 90nm ITO LED at 60m A injection current.The transmittance of ITO-M-Ga₂O₃ films at 365nm reaches92.68%and the sheet resistance is 20.1?/sq,which is 1.18 times higher than that of90nmITO films.At the same time,the light output power of the 365nmLED chip fabricated by ITO-M-Ga₂O₃ thin film can reach 15.29mW under the input current of 120mA,which is34.8%higher than that of 90nm ITO thin film with 11.34mW.The experimental results show that the M-Ga₂O₃ thin films have higher transmittance,lower sheet resistance and lower ohmic contact resistivity in the ultraviolet band.It has a good development prospect.