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Exciton localization and quantum efficiency - a comparative cathodoluminescence study of (In, Ga)N/GaN and GaN(Al,Ga)N quantum wells

Watson, I.M. and Jahn, U. and Dahr, S. and Brandt, O. and Grahn, H.T. and Ploog, K.H. (2003) Exciton localization and quantum efficiency - a comparative cathodoluminescence study of (In, Ga)N/GaN and GaN(Al,Ga)N quantum wells. Journal of Applied Physics, 93 (2). pp. 1048-1053. ISSN 0021-8979

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Abstract

We study the quantum efficiency () and transition energy (Et) as a function of excitation density and temperature in (In,Ga)N/GaN multiple quantum wells (MQWs) fabricated by molecular-beam epitaxy (MBE) and metal-organic chemical-vapor deposition (MOCVD), as well as in an MBE-grown GaN/(Al,Ga)N MQW. A method based on cathodoluminescence spectroscopy is proposed to be suitable for a reproducible measurement of the power dependence of and Et. The experimental results are fit to a recently developed model allowing for a distinction of localization and electric-field effects for and Et, as well as for the extraction of the localization energy, density of localization centers, and radiative recombination rate of localized excitons. In the (In,Ga)N/GaN MQWs grown by MBE and MOCVD, we found a value of the localization energy of 34 and 100 meV, respectively. In the MBE-grown GaN/(Al,Ga)N MQW, the exciton recombination is dominated by quasifree excitons even at low temperatures.