Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 69: Nitrides: LEDs

HL 69.5: Talk

Thursday, March 17, 2011, 11:15–11:30, POT 51

All-optical determination of absolute quantum efficiency values of GaInN-based light-emitters — •Bastian Galler, Matthias Sabathil, Ansgar Laubsch, Tobias Meyer, Lutz Höppel, Gertrud Kräuter, Hans-Jürgen Lugauer, Asako Hirai, Martin Straßburg, Matthias Peter, Andreas Biebersdorf, Ulrich Steegmüller, and Berthold Hahn — OSRAM Opto Semiconductors GmbH, Leibnizstraße 4, 93055 Regensburg, Germany

The efficiency droop of GaInN-based light-emitting diodes (LEDs) gets more and more significant for increasing wavelengths and thus contributes to the well-known green gap [1]. A major reason for this behaviour is that multi-quantum-well (MQW) operation is harder to achieve under electroluminescence conditions for LEDs with high indium content due to higher transport barriers. A possibility to circumvent this difficulty is optical pumping of a large number of green-emitting quantum wells. Using a UV-LED as an electrically driven pump for a green 40x MQW glued directly on its top, we show that this system can outperform direct green LEDs at large current densities. In addition to that, the combination of LED and converter platelet allows for an absolute quantum efficiency determination of the converter structure in contrast to conventional photoluminescence experiments. We use this method to obtain further evidence that the droop is due to a QW-internal loss process. Furthermore, we propose this approach as a general tool for the evaluation of other light-emitting structures that cannot be pumped electrically.

[1] T. Mukai et al., Jpn. J. Appl. Phys., Part 1 38 (1999).