Dresden 2017 – wissenschaftliches Programm
HL 25.10: Poster
Montag, 20. März 2017, 15:00–19:00, P2-OG2
Simulation of the temporal behavior of LEDs during fast modulation — •Dominic Kunzmann and Ulrich T. Schwarz — Chemnitz University of Technology, Experimental Sensor Science, Reichenhainer Str. 70, 09126 Chemnitz
In blue and green light emitting diodes (LEDs) based on InGaN quantum wells, the strain induced piezoelectric field and the field due to the built-in potential of the p-n junction causes a tilt of the band profile. The consequence is a red-shift of the emission (quantum confined Stark effect, QCSE) and reduction of the wave function overlap and consequently of the radiative recombination rate. Because the field of the p-n junction depends on the bias voltage, the radiative recombination rate can be modulated by the bias. In particular, a faster recombination is observed for zero or reverse bias . This results to a rapid increase in light intensity at the trailing edge of a driving pulse. Here we simulate the temporal behavior of the light emission during modulation with a rectangular driving current. We are interested in the time averaged internal quantum efficiency (IQE). We observe an increase of the IQE for a standard set of LED parameters. The maximum gain of several percent points was observed for driving frequencies of 0.2 GHz to 1 GHz for the chosen parameters.
References:  U. T. Schwarz et al., Interplay of built-in potential and piezoelectric field on carrier recombination in green light emitting InGaN quantum wells, Appl. Phys. Lett. 91, 123503 (2007).