* Corresponding author. Tel.: #49-721-608-3420; fax: #49- 721-607-593. E-mail address: heinz.kalt@physik.uni-karlsruhe.de (H. Kalt). Journal of Crystal Growth 214/215 (2000) 634}638 Stacking-fault-induced pairs of localizing centers in ZnSe quantum wells D. Lu K er{en, R. Bleher, H. Kalt*, H. Richter, Th. Schimmel, A. Rosenauer, D. Litvinov, A. Kamilli , D. Gerthsen, B. Jobst, K. Ohkawa, D. Hommel Institut fu ( r Angewandte Physik, Universita ( t Karlsruhe, 76128 Karlsruhe, Germany Laboratorium fu ( r Elektronenmikroskopie, Universita ( t Karlsruhe, 76128 Karlsruhe, Germany Institut fu ( r Festko ( rperphysik, Universita ( t Bremen, 28334 Bremen, Germany Abstract Pairs of bright spots are observed in microphotoluminescence intensity maps of ZnSe/ZnMgSSe quantum-well structures. These pairs are exactly aligned parallel to the [1 1 0] or [1  1 0] directions. Atomic-force microscopy and plan-view transmission electron microscopy reveal that the bright emission spots are related to pairs of stacking faults. The enhanced radiative recombination is a result of exciton localization in the region where the stacking faults intersect the quantum wells. Cross-section transmission electron microscopy and microphotoluminescence spectroscopy show that in the case of Frank-type stacking faults (oriented along [1 1 0]) the wells are enlarged by up to 12 bilayers. The exciton localization is much shallower in the case of Shockley-type stacking-fault pairs (oriented along [1  1 0]).  2000 Elsevier Science B.V. All rights reserved. PACS: 78.66.Hf; 61.72.Nn; 61.16.Bg; 68.35.Bs Keywords: ZnSe/ZnMgSSe; Quantum wells; Stacking faults; Microphotoluminescence; TEM; AFM Stacking-fault pairs originating at the II}VI/III}V interface are common defects in ZnSe- based heterostructures [1]. Two di!erent kinds of pairs are found: (1) pairs oriented along [1 1 0] which are bounded by Frank partial dislocations with b"  111 (b: Burgers vector or stacking- fault displacement vector), (2) pairs oriented along [1 1 0] which are bounded by Shockley partial dis- locations with b"  112. These extended defects are often discussed in connection with device failure of ZnSe-based laser diodes [2] but they are not the only cause for nonradiative recombination and de- vice degradation [3,4]. Stacking-fault pairs can even be the cause for enhanced radiative recombi- nation [5] as we will demonstrate in the following. We determined the structural and optical prop- erties of ZnSe/ZnMgSSe quantum-well structures by various methods with high spatial resolution: microphotoluminescence (-PL), atomic-force microscopy (AFM), and transmission electron microscopy (TEM). The investigated samples con- sist of ZnSe quantum wells (QW) embedded in Zn  Mg  S  Se  barriers. The Mg and S mole 0022-0248/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 0 0 ) 0 0 1 6 8 - 8