Design of Light Emitting Diodes (LED)E. Baur, M. Sabathil, and N. Linder
Osram Opto Semiconductors GmbH, Regensburg, Germany
For a proper design shaping of light emitting diodes, the exact knowledge of the current distribution in the active area is essential. On the one hand, one has to achieve a uniform current density over the chip area, on the other hand, one has to avoid current crowding in the neighborhood of the electrical contacts.
In this paper it is shown first how a LED can be modeled by COMSOL Multiphysics. The main problem here is to implement the nonlinear current-voltage characteristic with the use of two different domains. Second, the simulations are compared with experimental results.
The simulated voltage drop over the whole chip can be compared with the measured voltage drop on the top of the LED-contact-grid. Furthermore, the current density is immediately related to the optical power density generated and a comparison has been made between the simulated current density and the density distribution of the optical power across the chip.