Optimized Simulation of Nano-LED Far-Field Radiation Intensity and Emission Angle
Objective Nano-light emitting diodes(nano-LEDs)offer significant potential for ultra-high-resolution display applications.A key challenge in enhancing these displays is minimizing the emission angle of nano-LEDs to reduce optical crosstalk between adjacent pixels.This study addresses this issue by investigating the influence of various parameters on the emission characteristics of GaN-based nano-LEDs.Specifically,it explores the influences of nano-LED shape,the thickness of the GaN layer in the quantum well,and the surrounding dielectric layer on far-field radiation intensity and light emission angle.The objective is to provide a comprehensive simulation-based analysis that can guide the design and optimization of nano-LEDs for improved performance in high-resolution displays.Methods The study employs the finite element method(FEM)to simulate the optical behavior of GaN-based nano-LEDs.Several parameters are adjusted to analyze their effects on emission characteristics.First,different nano-LEDs are tested to determine their influence on the emission angle.Next,the thickness of the GaN layer within the quantum well is varied.Finally,the influence of a dielectric layer encasing the nano-LED is studied.Simulations are performed to evaluate both far-field radiation intensity and the vertical emission angle under these different configurations.The parameters are systematically adjusted to identify the optimal configuration that minimizes the emission angle and enhances the far-field radiation intensity.Results and Discussions To analyze the influence of nano-LED shape on emission properties,we compare the emission effects of nano-LEDs with various top diameters(D).As shown in Figs.1(d)-1(f),an electric field distribution for D=0,400,and 500 nm reveals that a top diameter of 500 nm results in a more focused electric field.The vertical emission angle of the cylindrical nano-LED,where the top and bottom diameters are equal,is smaller,indicating superior optical performance.Figures 1(g)-1(i)demonstrate that the far-field radiation intensity is maximized,and the vertical emission angle minimized when D=500 nm.This relationship is summarized in Figs.1(j)-1(k).Thus,a diameter of 500 nm is chosen for further optimization.Next,the effect of GaN thickness in the quantum well on the electroluminescence of cylindrical nano-LEDs with a diameter of 500 nm is examined.As shown in Figs.2(a)-2(d),increasing GaN thickness(T)enhances electron-hole recombination efficiency,leading to an expanded emission range,The electric field distribution for T=3,5,and 7 nm suggests that a thinner GaN layer(T=3 nm)maintains strong far-field intensity while minimizing the emission angle,as shown in Fig.2(e),which is ideal for achieving a smaller vertical emission angle.The addition of a dielectric layer around the nano-LED controls the effective emission area,focusing the light and improving its directionality.Figures 3(a)-3(d)show the electric field distribution for different dielectric layer widths(W=50,100,and 200 nm).A dielectric layer width of 200-300 nm is found to effectively absorb side-emitted light,reducing the emission angle and increasing far-field intensity by approximately 30%[Figs.3(e)-3(g)].The optimal width for minimizing the emission angle and maximizing intensity is found to be 70 nm.Further simulations investigate the effect of the dielectric layer's refractive index on emission properties.Figures 4(a)-4(d)illustrate the electric field distribution and far-field intensity for refractive indices ranging from n=1.3 to n=1.8,with W=200 nm.The optimal refractive index of n=1.5 provides the most focused far-field distribution and the smallest emission angle.A similar trend is observed for W=300 nm[Figs.4(e)-4(h)],where n=1.5 provides the best performance.Ultimately,cylindrical nano-LEDs with a dielectric layer of n=1.5 and W=300 nm demonstrate a significantly narrower emission angle and a 40%increase in far-field radiation intensity[Figs.5(a)and 5(b)].This configuration effectively absorbs side-emitted light and concentrates the emission,highlighting its potential for high-resolution display applications.Conclusions We analyze the factors influencing the emission characteristics of GaN-based nano-LEDs.Through FEM simulation,it is found that the top diameter,GaN layer thickness,and dielectric layer properties significantly affect far-field radiation intensity and emission angle.The optimal configuration,which includes a top diameter of 500 nm,a GaN layer thickness of 3 nm,a dielectric layer refractive index of 1.5,and a dielectric layer width of 300 nm,results in a 40%increase in far-field radiation intensity and a significantly reduced emission angle.These findings offer valuable insights for the design of high-performance nano-LEDs in ultra-high-resolution display applications.
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