Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 4: GaN: Preparation and Characterization I (mainly Optics)
HL 4.2: Vortrag
Montag, 26. März 2012, 09:45–10:00, EW 201
Evidence for strain-induced defects as dominant nonradiative recombination centers in GaInN/GaN quantum wells — •Torsten Langer, Markus Göthlich, Andreas Kruse, Holger Jönen, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — Institut für Angewandte Physik, TU Braunschweig
Via temperature-dependent time-resolved photoluminescence spectroscopy we investigate the recombination dynamics in low-pressure MOCVD-grown GaInN/GaN single and multiple quantum well (SQW, MQW) structures. The temperature dependence of the intensities and decay times is used to separate the effect of radiative and nonradiative recombination mechanisms with the aim to understand the dominant loss mechanisms in green light emitters. We previously showed that there is a strong shortening of nonradiative lifetimes at 300 K from >4 ns down to ≈100 ps when the indium concentration exceeds 25% in 5-fold QW structures. In this contribution we show evidence that these limiting loss mechanisms for green emitters are caused by strain-induced defects: The strain energy density increases with the square of the lattice mismatch towards higher indium concentrations. We observe an exponential shortening of nonradiative lifetimes with increasing cumulative 2D strain energy density. This holds both for MQW and for SQW structures. A mere growth temperature related defect (e.g. point defects due to poor dissociation of ammonia at low Tgrowth) is not consistent with our data.