Fabrication Of GaN-based Green Resonant Cavity Light-Emitting Diode And Its Directional Emission

Gallium nitride(GaN)-based light emitting diodes(LEDs)have the advantages of high efficiency and environmental-friendly,and have been widely used in solid-state lighting,display panels,optical communications,etc.With the growth of technology and the improvement of people’s living standard,the emerging 3D display technology,holographic imaging technology,virtual reality and augmented reality technology have higher requirements on the performance of light sources,such as higher integration,efficiency and stability,etc.GaN-based resonant-cavity light-emitting diodes have the characteristics of narrow emission spectrum,good directivity,stable emission wavelength,and the ability to drive optical metasurfaces,which can greatly expand the application of GaN-based LEDs.In this paper,we firstly studied a key fabrication technology of high-efficiency GaN-based RCLED—current blocking layer.The current blocking layer was fabricated on a traditional LED to improve the current distribution in the device and improve the luminous efficiency.The numerical simulations shows that the current blocking layer can effectively guide the current away from the etched sidewall,and the effective light-emitting area is equivalent to a common structure LED with the same size as the current blocking layer.The experimental results show that under the same light-emitting area,compared with ordinary structure LEDs,the current blocking layer can effectively improve the external quantum efficiency of the chips,from 5.0%to 14.6%,at the injected current density of 50A/cm~2.Next,a GaN-based RCLED was fabricated by applying the current blocking layer.The performance of devices with different sizes under various ambient temperature was measured.The results show that the wavelength shifts of the green RCLED are 0.02nm/m A and 0.03nm/K,which demonstrates that the luminescence wavelength of the RCLED has good temperature stability and current stability,which provides a stable platform for the application of lighting,display and communications.Finally,in order to further expand the application of RCLEDs,the performance of RCLEDs integrated with optical metasurfaces,taking the directional emission as an example,was studied.Based on the generalized Snell’s law,a phase gradient-controlled directional emission dielectric metasurface was designed.The numerical simulation shows that,for the incoherent spontaneous emission of LEDs,compared with the surface plasmon-based schemes,RCLED can achieve higher manipulation efficiency within a large light-emitting regions.The designed metasurface can manipulate the output light for 10°,20°,and 30°deflection,in which the deflection efficiencies are 46.66%,41.22%,and 31.69%,respectively.The RCLED chips with integrated metasurfaces can be applied to emerging technologies,such as holographic imaging and naked-eye 3D display.