Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 45: Group-III-Nitrides: Optical Properties II
HL 45.3: Vortrag
Mittwoch, 24. März 2010, 15:00–15:15, H15
Exciton enhancement of recombination mechanisms in GaInN/GaN quantum well structures — •T. Langer, A. D. Dräger, H. Jönen, D. Fuhrmann, H. Bremers, U. Rossow, and A. Hangleiter — Institute of Applied Physics, TU Braunschweig
Temperature-dependent and time-resolved photoluminescence spectroscopy on highly efficient GaInN/GaN quantum well structures with low excitation power reveal the nature of radiative recombination being free exciton dominated up to room temperature. This implies a strong enhancement of radiative recombination rates of free excitons compared to free carriers, due to a higher probability of electrons and holes being at the same place simultaneously. In the low excitation regime, where screening of excitons is not important, we therefore observe a linear rather than a quadratic carrier concentration (n) dependence of radiative recombination rates. This observation, as well as the radiative rates in the whole temperature and carrier concentration range, can be described using a n-dependent correlation function geh of electrons and holes in a many body system. The radiative recombination rate turns to B geh(n) n2 in case of optical excitation (n=p).
We also discuss the effect of excitons on Auger recombination, whose rate is known to be proportional to n3 for free carriers. For GaInN/GaN quantum well structures, the Auger coefficient is about 1 · 10−31cm6s−1 which appears to be too low to let Auger recombination become a significant recombination process in such structures. Nevertheless, excitonic enhancement might increase the importance of Auger recombination in these materials.