Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 52: Nonpolar and Semipolar Nitrides
HL 52.3: Vortrag
Mittwoch, 16. März 2011, 12:15–12:30, POT 51
Polarisation of the spontaneous emission from nonpolar and semipolar InGaN quantum wells — •Lukas Schade1,2, Ulrich Schwarz1,2, Simon Ploch3, Tim Wernicke3, Arne Knauer4, Veit Hoffmann4, Markus Weyers4, and Michael Kneissl3,4 — 1Department of Microsystems Engineering, University of Freiburg (IMTEK) — 2Fraunhofer Institute for Applied Solid State Physics (IAF) — 3Institute of Solid State Physics, Technical University Berlin — 4Ferdinand-Braun-Institute, (FBH)
Spontaneously emitted light stemming from semipolar and nonpolar InGaN quantum wells is polarized. This property is a consequence of the broken in-plane symmetry of non c-plane wurtzite quantum wells. We studied the polarized photoluminescence of semipolar and nonpolar InGaN/InGaN multi quantum wells grown on low defect density GaN substrates with a setup for confocal microscopy. For excitation of charge carriers we use a 375 nm diode laser. The photoluminescence is collected with an objective of small NA, to avoid polarisation scrambling, and analyzed with a broadband polarizer and a spectrometer. The experimental results are compared to k·p band structure calculations for semipolar and nonpolar InGaN quantum wells. These simulations provide the polarisation degree of the confined states of the valence band and their energetic splitting. Next, from the thermal occupation the polarized spectra are calculated. The comparison with experimental results allows the determination of the valence subband splitting. Our experiments show a splitting of the two topmost valence subbands in nonpolar direction which is larger than predicted.