SpeCLED – 3D Modeling of Current Spreading and Temperature Distribution in LED chip

SpeCLED (Spreading of Current in Light-Emitting Diodes) is a software for modeling of the current spreading and heat transfer in planar and vertical LED chips. As a part of the task, it simulates distribution of the current density, internal quantum efficiency (IQE), and the temperature over the active region. SpeCLED also computes a number of integral characteristics of the device such as the forward voltage, output emission power, wall-plug efficiency, etc. as a function of the forward current.

LED chip is considered in the SpeCLED as one fabricated by planar technology operations. This allows the layer-by-layer input of the actual 3D chip geometry, which makes it much easier to set up a simulation case. A prismatic grid, unstructured/structured in plane, is generated either automatically or manually. User can change the grid refining, if necessary. Different blocks in the grid are recognized automatically and their properties are identified from the description of the constituent layers. A complex structure of semiconductor layers, including non-uniform doping and composition, may be specified via user scripts.

Basic design of 815×875 μm2 blue LED die

Basic design of 815×875 μm2 blue LED die

A 3D model is employed to simulate the current spreading in the quasi-neutral regions where carrier drift dominates over diffusion. The active region is considered as an in-plane distributed non-linear resistor with known temperature-dependent j-U characteristics relating the local normal current density j with the p-n junction bias U applied to the active region. These characteristics may be either defined manually or imported from external files. So, the j-U characteristics can be taken from 1D simulations by SiLENSe.

Specification of the LED die geometry

Specification of the die geometry

Automatic generation of the computational grid

Automatic mesh generation

The current spreading in metal electrodes/pads and semitransparent ITO layers is considered in SpeCLED self-consistently. The heat transfer analysis coupled with the current-spreading problem provides the temperature distribution inside the LED chip. The heat generation inside the chip is found with account of the current density distribution obtained from the current-spreading problem. The temperature effect on the active region characteristics, as well as on the impurity ionization in thick semiconductor layers is considered in simulations.

Files with results of computations generated by SpeCLED package can be used as input data for RATRO, a 3D ray-tracing simulator of the light extraction from the LED chip.

Current density distribution in the active region od an LED die

Current density distribution in the active region

2D distribution of Internal Quantum Efficiency

2D distribution of Internal Quantum Efficiency

Key Publications

Sergey Yu. Karpov
“Modeling of III-nitride Light-Emitting Diodes: Progress, Problems, and Perspectives”, Proc. of SPIE, vol. 7939 (2011) 79391C / DOI 10.1117/12.872842

M. V. Bogdanov, K. A. Bulashevich, O. V. Khokhlev, I. Yu. Evstratov, M. S. Ramm, and S. Yu. Karpov
“Current crowding effect on light extraction efficiency of thin-film LEDs”, phys. stat. solidi (c) 7, No 7–8, 2124–2126 (2010)

M. V. Bogdanov, K. A. Bulashevich, O. V. Khokhlev, I. Yu. Evstratov, M. S. Ramm, and S. Yu. Karpov
“Effect of ITO spreading layer on performance of blue light-emitting diodes”, phys. stat. solidi (c) 7, No 7-8, 2127–2129 (2010)

K. A. Bulashevich, O. V. Khokhlev, M. V. Bogdanov, M. S. Ramm, I. Yu. Evstratov, and S. Yu. Karpov
“Comparison of Alternative Approaches to High-Power Thin-Film LED Chip Design”, Proceedings of the Second International Conference on White LEDs and Solid State Lighting, Taipei (2009)

M.V. Bogdanov, K.A. Bulashevich, I.Yu. Evstratov, S.Yu. Karpov
“Current spreading, heat transfer, and light extraction in multipixel LED array”, phys. stat. solidi (c) 5, No. 6, 2070–2072 (2008)

K.A. Bulashevich, I.Yu. Evstratov, V.F. Mymrin, S.Yu. Karpov
“Current spreading and thermal effects in blue LED dice”, phys. stat. solidi (c) 4, No. 1, 45–48 (2007).

 

Vectors of electric current in selected horizontal cross-section

Vectors of electric current in selected horizontal cross-section