ELSEYIER Journal of Crystal Growth 184/185 (1998) 311-314 Three-dimensionally confined excitons in MOCVD-grown ultrathin CdSe depositions in ZnSSe matrix R. Engelhardt”,*, V. Tiirck”, U.W. Pohl”, D. Bimberg”, P. Veitb aInstitut zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA fir FestkSrperphysik, Technische Uniuersitiit Berlin, 10623 Berlin, Germany bInstitut fir Experimentelle Phvsik, Otto-uon-Guericke Universittit Magdeburg, 39016 Magdeburg, Germany Abstract Up to 3 monolayer (ML) thick highly strained CdSe insertions in lattice matched ZnSSe/GaAs were grown by metalorganic chemical vapor deposition (MOCVD). The samples show a bright photoluminescence band near the barrier band edge exhibiting a strong red shift with increasing CdSe deposition. The assignment to recombinations of three-dimensionally confined excitons is confirmed by cathodoluminescence. An additional-low energy band appearing for thicker CdSe depositions is attributed to defects. 0 1998 Elsevier Science B.V. All rights reserved. PACS: 78.55.Et; 78.60.Hk; 78.66.Hf Keywords: CdSe/ZnSSe; Quantum dots; MOCVD; Cathodoluminescence 1. Introduction Zero-dimensional semiconductor structures are of great interest due to their large potential for applications in micro- and optoelectronics. Self- organized formation of quantum dots with small size distribution is now established for highly strained III-V heterosystems [1,2]. Evidence for exciton localization in (Zn,Cd)Se-related MBE- grown structures on GaAs( 1 0 0) [3-71 as well as on GaAs(1 1 0) [8] and ZnSe(1 1 0) [9] surfaces has *Corresponding author. Fax + 49 30 314 22569; e-mail: engel@w422zrz.physik.tu-berlin.de. been recently reported by several groups. Details of the structural properties, formation of a wetting layer and transition energy of dot-like structures are, however, controversial. 2. Experimental procedure ZnSSe/CdSe/ZnSSe samples were grown by MOCVD at 100 mbar total pressure using DMZn- TEN, DTBSe, tBSH and DMCd precursors. CdSe was typically deposited on a 50 nm thick ZnSSe buffer layer lattice matched to the GaAs(1 0 0) sub- strate and overgrown by a 20 nm thick ZnSSe cap layer. The samples were grown at a temperature of 0022-0248/98/$19.00 p 1998 Elsevier Science B.V. All rights reserved PII SOO22-0248(97)007 1 O-O