SimuLED—engineering tool for LED and laser diode design and optimization

Application example: Modeling of Surface Recombination in Micro-LEDs

In brief, SimuLED capabilities include coupled simulation of:

  • carrier transport in the heterostructure and LED spectrum;
  • current spreading/crowding in LED die;
  • heat transfer in LED die;
  • light extraction from the LED die.

The SimuLED software is based on a multi-scale approach to LED and LD modeling. The simulator can be used for design and optimization of devices based on group-III nitrides and other wurtzite materials as well as hybrid structures​. The drift-diffusion model is applied to the carrier transport, recombination, and light emission in the heterostructure, while the current spreading in an LED/LD die is simulated using the 3D hybrid approach. This makes computations very fast while reflecting the essential physics of processes occurring in the LEDs/LDs. The self-heating and current spreading in the die are simulated self-consistently which is especially important for optimization of high power devices and micro LEDs. The SimuLED package consists of three compatible software tools: SiLENSe, SpeCLED, and RATRO:

The SiLENSe package is designed for 1D drift-diffusion analysis of electron and hole injection into the active region, and their radiative and non-radiative recombination. All important recombination channels are taken into account, including Auger recombination and recombination on threading dislocations inherent in Group-III nitride heterostructures. The software predicts the current density as a function of local bias applied to the p-n junction and provides such important characteristics as internal quantum efficiency (IQE), emission spectrum, and detailed information on the carrier distribution across the heterostructure. SiLENSe is a tool for heterostructure development and optimization, and can be useful for both device and epitaxy engineers.

The SpeCLED package provides 3D analysis of current crowding and temperature distribution in the LED dice fabricated on either insulating or conductive substrate. It supports simulation of planar and vertical chips with one-side and two-side electrode configurations. The package enables optimization of both blocking and ITO-like spreading layers that have become important units of advanced LED chips. SpeCLED uses the computational results obtained by SiLENSe to specify the current density as a function of local values of bias and temperature at each fragment of the active region and supposes Ohmic behaviour of neutral contact layers far from the active region. This tool is widely used for optimization of contact electrode geometry and predicts the actual temperature of the active region as a function of operation conditions.

RATRO (Ray-Tracing Simulator of Light Propagation) is a 3D ray-tracing simulator of light propagation, absorption, and extraction from the LED die. The RATRO package uses the data on non-uniform light emission intensity distribution in the LED active region obtained by SpeCLED. Then the package computes the light intensity distribution over all the die surfaces, the far-field distribution, and integral chip characteristics like extraction efficiency, total light output, light polarization, etc. The ray-tracing model accounts for the light refraction, reflection, and absorption on both smooth and rough surfaces/interfaces, multiple layer coatings and DBRs, using advanced optical models of regular/random surface patterning.