Light extraction in planar light-emitting diode with nonuniform current injection: model and simulation

Abstract

We develop an analytical and numerical model for performing simulation of light extraction through the planar output interface of the light-emitting diodes (LEDs) with nonuniform current injection. Spatial nonuniformity of injected current is a peculiar feature of the LEDs in which top metal electrode is patterned as a mesh in order to enhance the output power of light extracted through the top surface. Basic features of the model are the bi-plane computation domain, related to other areas of numerical grid (NG) cells in these two planes, representation of light-generating layer by an ensemble of point light sources, numerical "collection" of light photons from the area limited by acceptance circle and adjustment of NG-cell areas in the computation procedure by the angle-tuned aperture function. The developed model and procedure are used to simulate spatial distributions of the output optical power as well as the total output power at different mesh pitches. The proposed model and simulation strategy can be very efficient in evaluation of the output optical performance of LEDs with periodical or symmetrical configuration of the electrodes.

Computational Modeling of Planar Light-Emitting Diode with Mesh-Like Electrode

“…We consider three approaches of total output power calculations: (a) present procedure, (b) present procedure without thick (9000nm) air layer for finite element solution, and (c) present procedure with the analytical potential introduced in [4].…”

“…BY FINITE ELEMENT SOLUTION WITH MLS RESAMPLING, AND THE SECOND ROW SHOWS THOSE OF ANALYTICAL SOLUTION IN [4] FIGURE V. COMPARISONS OF POWER DENSITY DISTRIBUTION AT THE INTERFACE OF SEPARATION LAYER AND THE TOP METAL ELECTRODE LAYER. THE FIRST ROW SHOWS DISTRIBUTIONS USING PRESENT MODEL, AND THE SECOND ROW SHOWS RESULTS USING [4] V. CONCLUSION A computational procedure is developed for modeling an LED with mesh like top metal electrodes. The finite element method is applied to obtain the potential energy distribution, and it is resampled by the moving least squares approximation.…”

“…The enhancement of optical output was related to potential profile created by meshed electrode in the plane of pn-heterojunction [3]. It is expected that a peak output can be obtained at a certain range of the mesh pitches Light generation and extraction in the LED with nonuniform current injection was considered in [4], where the strips of the mesh-like metal electrode were represented by the circular cross sectional wires of finite radius. However, the model has some limitations; in particular, it does not allow to vary individually the width or thickness of the strips.…”

“…The electric potential distribution can be obtained from a solution of Laplace equation with voltage applied to the meshed top electrodes as boundary conditions. The saturation current density J0 may be estimated from a set of physical parameters or from the injected current measured as a current in the external circuit[4].…”