Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 63: Devices I

HL 63.7: Talk

Wednesday, March 28, 2012, 16:30–16:45, EW 015

Effect of temperature and strain on the optical polarization of ultraviolet light emitting diodes — •T. Kolbe¹, A. Knauer², V. Kueller², J. Stellmach¹, C. Chua³, Z. Yang³, S. Einfeldt², P. Vogt¹, N.M. Johnson³, M. Weyers², and M. 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 temperature and strain dependence of the optical polarization of the in-plane electroluminescence (EL) of (0001) oriented (In)(Al)GaN multiple quantum well (MQW) LEDs has been investigated. The EL measurements show a decrease of the emission intensity for transverse-electric (TE) polarized light relative to the transverse-magnetic (TM) polarization with decreasing emission wavelength. This can be explained by a change of the order of the heavy, light and split-off hole band in the (In)(Al)GaN active region with a changing Al-content. With increasing sample temperature it was found that the TM polarized part of the emission increases for LEDs with a dominant TE polarized emission (and inverted) because the occupation probability of high-energetic bands increases with increasing temperature. We further investigate the influence of the strain in the MQWs on the optical polarization of near UV LEDs. It was observed that the TM polarized part of the emission clearly increases if strain of the MQWs is reduced by a change of the barrier material between the quantum wells.