Study On The Effect Of Nano-etching Of P-type Layer On The Luminescence Efficiency Of GaN-based UV LED

In recent years,GaN-based light-emitting diodes(LEDs)have attracted increasing attention due to their advantages of low energy consumption,environmental protection,long lifetime,and small size.They are widely used in full-color displays,traffic lights,solid-state lighting and other fields.However,the luminous efficiency of GaN-based LEDs still needs to be further improved,but the problem of low external quantum efficiency still needs to be overcome.The key issue is how to solve the problem of low light extraction efficiency(LEE)caused by the total reflection angle between GaN and air interface.This paper focuses on the research of improving the light extraction efficiency of LEDs based on the single-layer colloidal crystal-derived nanopit structure,using metal organic chemical vapor deposition(MOCVD)to grow In GaN/GaN multi-quantum well structure LEDs on the sapphire c surface to prepare silicon dioxide nanospheres monolayer films,and apply them to the surface of the GaN-based LED to mask etching so as to realize chip surface patterning and enhance the light extraction efficiency of the LED.The method of preparing nanosphere monolayer masks is a hot focus and difficulty in current research.In this paper,two experimental methods spin-coating and dip-drop for coating nanospheres are designed to find the optimal high-quality silicon dioxide nanospheres monolayer array arrangement.The morphological analysis of the silica nanospheres obtained by metallographic microscope and SEM,and study found that:(1)The concentration of Si O₂ nanospheres in the self-assembly process of the spin coating method affects the thickness of the film formed by self-assembly;The dilution ratio of the suspension solvent controls the volatility and ductility of the Si O₂ nanosphere solution;the rotational acceleration of the homogenizer provides a twisting force for the Si O₂nanosphere suspension and reduces the Si O₂ nanosphere splashing outside the substrate.(2)The volume of suspension used in the self-assembly process of the dip-drop method will reach saturation within a certain range;the addition of dispersant changes the physical and chemical properties of the surface of the Si O₂ nanospheres,can produce compatibility with organic matter,and improve the Si O₂ nanospheres dispersibility;The addition of SDS surfactant changes the interface state of the solution surface,making the nanospheres more tightly arranged at the gas-liquid self-assembly interface.Though the comparison of the two best results,it was concluded that the dip-drop method formed the hexagonal close-packed structure and the single-layer array is the best.From the perspective of factors that affect the light extraction efficiency of GaN-based LEDs,the author further designed a silicon dioxide nanospheres monolayer array as a mask,and used top-down ICP etching technology to prepare periodic nano-patterned in the P-GaN layer of LED.The etched nano-patterned structure of GaN exhibits presented stress relaxation,and the light extraction efficiency of LEDs with nano-pit pattern surfaces was greatly affected compared to flat-sheet LEDs.Shallow etching depth can prevent the conversion of the spontaneous emission of the composite guided mode of the carriers in the LED,and can also enhance the coupling effect of the nano-patterned on the guided mode.If the etching depth is too deep,the nano-patterned will damage the active layer and the photon state density in the active layer will be greatly reduced,resulting in a reduction in carrier radiation recombination rate.Therefore,it is necessary to optimize the etching depth,and find out the depth under the condition of optimal comprehensive characteristics such as luminous performance and withstand voltage characteristics are optimal depth.Considering that the etching depth has a great influence on the luminescence efficiency of the LED,the paper designed three experiments with different etch depths,analyzed the influence of the etch depth on the epitaxial wafers from the changes in the surface stress and luminous intensity of the samples,and made the devices for photoelectric performance testing,and analyzed the different etched according to the test results.The experimental results of this paper show that the use of silicon dioxide nanospheres monolayer etching can effectively improve the LED light extraction efficiency(At 20m A injection current,the increase in optical output power can reach 11.7%).In this paper,a high-quality silicon dioxide nanospheres monolayer array is obtained and a relatively good etching depth of 150nm is found by optimizing the experimental parameters,thereby improving the luminescence efficiency of the LED,and further giving a certain direction for the research on improving the luminescence efficiency.