Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 69: Nitrides: LEDs

HL 69.1: Vortrag

Donnerstag, 17. März 2011, 10:15–10:30, POT 51

Optical polarization of UV-A and UV-B (In)(Al)GaN multiple quantum well light emitting diodes — •Tim Kolbe¹, Arne Knauer², Joachim Stellmach¹, Chris Chua³, Zhihong Yang³, Sven Einfeldt², Patrick Vogt¹, Noble M. Johnson³, Markus Weyers², and Michael Kneissl^1,2 — ¹Institute of Solid State Physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany — ³Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA 94304, USA

The optical polarization of the in-plane electroluminescence of (0001) oriented (In)(Al)GaN multiple quantum well light emitting diodes (LEDs) in the spectral range from 288 nm to 386 nm has been investigated. A decrease of the intensity of transverse-electric (TE) polarized light relative to transverse-magnetic (TM) polarized light with decreasing emission wavelength is found. This effect is attributed to rearrangement of the valence bands at the gamma-point of the Brillouin zone with changing aluminum and indium mole fractions in the (In)(Al)GaN quantum wells. For shorter wavelengths the crystal-field split-off hole band moves closer to the conduction band relative to the heavy and light hole bands. As a consequence TM polarized emission from the split-off hole band becomes more dominant for LEDs with a decreasing emission wavelength. A polarization of zero (that means that the intensities of the TE polarized light and the TM polarized light are the same) is found for LEDs emitting near 300 nm. For shorter wavelengths the emitted light is mainly TM polarized.