Realization Of 650nm Micro-RCLED Working At Low Driving Current For Micro-Displays

At present,red-light Micro-LEDs play an increasingly important role in the display field.In order to obtain high-contrast and high-color rendering full-color RGB microdisplays,in addition to high-efficiency blue/green light Micro-LEDs,high-efficiency red light Micro-LED is also essential.However,due to the substrate absorption,current congestion,and internal reflection effects of AlGaInP red LEDs,the efficiency of red Micro-LEDs is generally low.This paper proposes a micro-high efficiency red LED with a resonant cavity structure,namely Micro-RCLED.The main contents are summarized as follows:(1)Analyze the research status of the current display field.Introduce the research status of Red/Green/Blue tri-color Micro-LED,and focus on the problems of low luminous efficiency and unstable peak wavelength change of Red Micro-LED,and propose to use RCLED instead of traditional AlGaInP LED as Micro-LED Light source.Then introduced the principle and research status of 650nm red RCLED,and finally explained the theoretical advantages of RCLED as a Micro-LED light source to replace the traditional AlGaInP group.(2)Analyze and design the red light Micro-RCLED device.Based on microcavity theory and thin-film optical transmission matrix model,RCLED epitaxial structure is grown on N-type GaAs substrate,including 30 pairs of N-type Al_0.5Ga_0.5As/AlAs DBR,1 AlGaInP optical resonator,6 pairs of P-type AlGaAs DBR,And 5 nm p⁺GaAs contact layer.Among them,the central reflection wavelength of the DBR and the resonance wavelength of the resonant cavity are both650 nm.The pair of P-type DBR near the cavity is AlAs/Al_0.5Ga_0.5As for lateral oxidation,and the other five pairs are Al_0.9Ga_0.1As/Al_0.5Ga_0.5As,in the center of the cavity are three Ga_0.5In_0.5P/(Al_0.5Ga_0.5)In_0.5P quantum wells as the light-emitting active area,the thickness of the well and the barrier are 5nm.Then,the preparation process design of the red-light Micro-RCLED device is carried out,starting from improving the efficiency of injecting the carrier,through the design of the second mesa and the N-P-DBR average oxidation method.And formulate the post-process flow,design the small mesa,large mesa,isolation layer and stripping electrode process.In order to ensure the implementability of the process,it is proposed to take the large mesa of the three-unit light-emitting point as a whole and etch it out by ICP,and finally design Developed a photolithographic layout.(3)Optimized the main technological process of Red Light Micro-RCLED.The important links and difficulties in the photolithography,ICP,etching,wet nitrogen oxidation and thick Au stripping processes are elaborated.Through reasonable masks and configuration of ICP etching parameters,the target size table is obtained,and the oxidation is used In the furnace,the oxidation time and temperature were precisely controlled,and a three-unit red-light Micro-RCLED chip with an optical aperture of17?m and a single-electrode red-light Micro-RCLED chip with an aperture of 21?m were prepared.Finally,the double-layer adhesive stripping electrode process was used to successfully strip 150/6000(?)Ti/Au.Finally,the epitaxial wafer is thinned to 150?m,and a red-light Micro-RCLED with excellent performance is prepared and encapsulated on a special tube base.(4)Tested and theoretically analyzed the prepared three-unit die and single-point die.Three-cell die results show that the device can observe the red light visible to the naked eye at a minimum of 2?A.When 1m A is injected,the device optical power reaches 0.21m W,and the external quantum efficiency(EQE)is 10.9%.Full width at half maximum(FWHM)changes only 0.33nm with the increase of current,reaching a maximum of 13.263nm.Through the aging experiment that has been lit up,it has also been found that the red-light Micro-RCLED has been very stable.The final result shows that it is possible to use RCLED as a monochromatic light source in Micro-LED.