Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 56: Non- and Semi-polar Group-III-Nitrides
HL 56.2: Vortrag
Donnerstag, 25. März 2010, 14:15–14:30, H15
Polarization-dependent photoluminescence studies of semipolar and nonpolar InGaN quantum wells — •Lukas Schade1, Ulrich Schwarz1, Tim Wernicke2, Markus Weyers2, and Michael Kneissl2,3 — 1IAF, Freiburg, Germany — 2FBH Berlin, Germany — 3Institute of Solid State Physics, TU Berlin, Germany
Light emitted from optical devices based on semi- and nonpolar GaN quantum well (QW) structures is partially or totally polarized, as a consequence of crystal symmetry and band structure. This can be an additional advantage over polar (0001) GaN in specific applications, e.g. in LED backlighting. Fundamentally, the polarized emission stems from breaking the isotropic symmetry of the hexagonal c-plane, resulting in two discrete semi- and nonpolar directions (parallel and normal to the projection of (0001)). We use the k.p method to simulate the crystal-direction dependent emission. The resulting transition matrix elements assign a specific (partial) polarization for each subband. The thermal occupation of the subbands results in a temperature dependent effective polarization of the light emission. We study MOVPE grown homoepitactical polar, semi- and nonpolar samples, measuring the polarization properties of the resonantly excited photoluminescence from the QW. With the complete polarization of the subbands for nonpolar devices it is possible to measure the energetic difference of the first two valence band levels. In contrast to our calculations we find a higher degree of polarization also in semipolar directions. A possible explanation could be a higher energetic subband difference than computed.