Design And Performance Simulation Of GaN Based Single Chip White LED

With the vigorous development of the third-generation semiconductor industry and the continuous breakthrough of related technologies,the new solid-state lighting industry dominated by gallium nitride(GaN)-based light-emitting diodes(LEDs)has risen rapidly in the world,becoming the commanding heights of technology and industry that various countries compete for.In recent years,countries have successively introduced development plans and corresponding development incentive policies for the technical research of GaN-based LED lighting industry,so that their industries have gradually matured.In addition to the characteristics of long life and small size,the advantages of energy saving and environmental protection of GaN-based white LED semiconductor lighting are of great strategic significance for the conservation of global resources and the development of societyThe production method of single-chip GaN-based white LED is divided into blue LED excitation phosphor YAG(yttrium aluminum garnet)emitting yellow light or doping carbon atoms to the blue active region to emit yellow light,and the two are mixed to produce white light;Blue light and yellow-green light quantum well structure cascade,and then mixed to produce white light,and the active region InGaN phase separation to produce different wavelengths of light,and then mixed to produce white light.Considering energy efficiency and other issues,the current manufacturing process of GaN-based white LEDs on the market is still based on the first method.However,due to the aging problem of phosphors,the life of white LEDs will be shortened,and the color rendering index of white LEDs will be reduced over time.Therefore,the single-chip GaN-based white LED designed in this paper adopts the method of quantum well cascade,first cascading the blue LED and the yellow-green LED on the same chip,using GaN as the barrier layer to separate the blue light from the yellow-green light,and then aiming at the problem of lattice mismatch between the potential well layer and the barrier layer,the traditional InGaN/GaN quantum well structure with constant In components is changed to a quantum well structure with gradient In components.By changing the In component and thickness of the quantum well of the gradient layer,the device performance of the LED is calculated and analyzed,and the structure of the LED quantum well is optimized,the lattice mismatch between the barrier layer and the potential well layer is reduced,and the internal quantum efficiency is improved.The main work of this article is as follows:(1)Single-chip white light needs to be produced by mixing blue light with yellow-green light,that is,the quantum well InxGa1-xN/GaN of different In components is excited by blue light and yellow-green light,and GaN is used as a barrier layer to separate the high In component from the low In group.Yellowgreen light is excited by blue light,so the quantum efficiency and photon energy requirements of blue LED are higher.In view of the above problems,this paper designs the GaN-based LED gradient layer quantum well structure,and calculates and analyzes the influence of the material and structure of the gradient layer on the device performance by modeling and simulating this structure in Silvaco Atlas software,including the uniform growth of the single layer In component of the gradient layer.The top In component of the gradient layer grows;the thickness of the top layer of the gradient layer;Effect of non-top thickness of gradient layer on polarized charge density,carrier concentration,and power spectral density.By introducing the gradient layer structure,the polarization effect problem of InGaN/GaN quantum well structure is effectively alleviated.(2)The generation of yellow-green light requires a quantum well with high In composition,but too high in the In component of the potential well layer will tilt the energy band between the barrier layer and the potential well layer,reduce the overlap of electrons and holes in space,resulting in reduced luminous efficiency.Therefore,for the yellow-green light band,the gradient layer quantum well structure is still adopted to reduce the polarization effect caused by the high in component InxGa1-xN/GaN quantum well and improve the power spectral density.In addition,the mobility of holes is low relative to electrons,and the recombination of electrons and holes is usually in the last region of the quantum well,and studies have shown that P doping of InGaN/GaN quantum well structures can effectively enhance the luminescence performance of LEDs.Therefore,in this paper,the last region of the high-In component quantum well is P-doped,and the material and thickness are changed,and the effect on the performance of yellow-green LED devices is calculated and analyzed.After optimizing the material and structure data of the potential well layer,the optimal data is taken,the thickness of the barrier layer is changed,and the power spectral density of blue light and yellow-green light is calculated.Then,the color coordinates of blue light and yellow-green wavelengths of different materials and structural parameters of the potential well layer are calculated,and the position of the mixed color light is marked on the CIE(International Commission on Illumination)chromatic map.In this thesis,aiming at the aging of single-chip GaN-based white LED phosphors,the structure of GaN-based single-chip white LED with gradient layer quantum well without phosphors is designed,and the LED structure is modeled and simulated by Silvaco Atlas software,and the calculation shows that the gradient layer quantum well structure can effectively alleviate the polarization effect caused by high In components,reduce non-radiative recombination,and increase the internal quantum efficiency.Aiming at the problem of "yellow-green gap" in the yellow-green light band,the material and structural parameters of the potential well layer with high In components are modeled and simulated,and the position of mixed white light is determined by calculating the blue light and yellow-green light color coordinates.The research results have important guiding value for the design and development of dual-primary color single-chip GaNbased LEDs.