Eur. Phys. J. B (2013) 86: 221
https://doi.org/10.1140/epjb/e2013-30957-x

Regular Article

Homogeneous broadening and k-vector conservation in direct bandgap transitions

Non-Lorentzian homogeneous line shapes for exponential decays under relaxation time approximation

¹ Consulting Photonics Scientist, Espoo, FIN-02180, Finland
² Coherent Inc., Santa Clara, CA 95054, USA

^a e-mail: juha.viljanen@iki.fi

Received: 20 October 2012
Received in final form: 19 February 2013
Published online: 16 May 2013

Abstract

k-vector conservation is studied in direct bandgap optical transitions by examining edge emitted photoluminescent and electroluminescent spectra. Inhomogeneously and homogeneously broadened spectra are identified in tensile strained, single quantum well, broad stripe laser diode structures. In low excitation conditions, the molecular beam epitaxy (MBE) deposited test structures showed Urbach-tail like inhomogeneous broadening with small Urbach parameter values, typical for high quality materials. At high excitation conditions, significant deviations from Lorentzian line shape were observed and concluded to arise from k-vector conservation within the line broadening process.