,oumwuo~ zyxwvutsrqponmlkjihgf CRYSTAL aROWTH zyxwvutsrqpo EJ-SEVIER Journal of Crystal Growth 184/185 (1998) 886-889 Interface roughness correlation in CdTe/CdZnTe strained quantum wells N.T. Pelekano+*, N. BoudeF, J. Eymery”, H. Marietteb a zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Dipartement de Recherche Fondamentale sur la Matidre Condensie. CEAIGrenoble, SPZMIPSC, 17 rue des Martyrs, 38054 Grenoble, France ‘Laboratoire de Spectromktrie Physique, CNRS, Universiti J. Fourier, 38042 Grenoble, France Abstract In CdTe/CdZnTe strained quantum wells (QWs) the exciton inhomogeneous linewidth decreases with decreasing QW width. We interpret this unusual behaviour as a manifestation of the fact that the two QW heterointerfaces are increasingly correlated for narrow QWs, resulting in reduced well width fluctuation along the QW plane. Small incidence angle X-ray diffraction experiments confirm this interpretation. 0 1998 Elsevier Science B.V. All rights reserved. PACS: 78.66. - w; 78.66.Hf; 71.35. - y; 61.10. -i Keywords; Interface roughness correlation; Exciton linewidths; Strained heterostructures The excitonic lines of semiconductor quantum wells (QWs) are typically inhomogeneously broadened at low temperature. For single QWs the main cause of inhomogeneous broadening is QW width fluctuations along the QW plane [l]. As the QW width L decreases, a given width fluctuation induces a larger variation of the confinement energy, and thus the exciton inhomogeneous linewidth rinh increases for narrower QWs. This has been systematically observed in a large variety of QW systems, including the GaAs/AlGaAs one [1,2]. In this report, we present results on CdTe/CdZnTe single QWs showing the exactly op- *Corresponding author. Fax: + 33 476 88 50 97; e-mail: npelekanos@cea.fr. posite behaviour, namely, as L decreases rinh also decreases. For the optical measurements, a series of single CdTe/Cdo.s6Zno.r4Te ,QW samples with varying L between 25 and 130 A were grown coherently by MBE on nominal (1 0 0)Cd0.asZn,,12Te substrates. It should be noted that the CdTe QW layer is under compression (E = - 0.7%) whereas the barrier layers are under weak dilation (E = + 0.12%). All rinh values reported here were measured in either photoluminescence (PL) or transmission experi- ments, the two techniques offering almost identical results. In Fig. 1, we compare the T = 2 K PL spectra, obtained under identical excitation conditions, of two single QWs (grown during the same run and on a single substrate) with L = 130 and 30 A. The 0022-0248/98/$19.00 c’ 1998 Elsevier Science B.V. All rights reserved. PII SO O 22- 0248(97)00646- 5