Physica B 272 (1999) 518}521 Strong exciton binding in hybrid GaAs-based nanostructures Guido Goldoni *, Fausto Rossi, Elisa Molinari Istituto Nazionale per la Fisica della Materia (INFM) Modena, Italy Dipartimento di Fisica, Universita % di Modena, Via Campi 213/A, 41100 Modena, Italy Dipartimento di Fisica, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy Abstract We propose a new type of hybrid systems formed by conventional semi-conductor nanostructures with the addition of remote insulating layers, where electron}hole interaction is enhanced by combining quantum and dielectric con"nement over di!erent length scales. Due to the polarization charges induced by dielectric mismatch at the semiconduc- tor/insulator interfaces, the exciton binding energy can be strongly enhanced. By a novel theoretical scheme, we show that, for realistic structures based on conventional III}V quantum wires, such remote dielectric con"nement allows exciton binding at room temperature.  1999 Elsevier Science B.V. All rights reserved. PACS: 78.66.Fd; 73.20.Dx; 71.35.!y; 77.55.#f Keywords: Quantum wires; Exciton; Hybrid structures The electron}hole Coulomb interaction in semiconductors leads to bound excitonic states that could play a crucial role in the next generation of optical devices. For this purpose, however, the binding energy E  must exceed the thermal energy at room temperature, a condition that is not yet met in conventional III}V materials. In fact, a large enhancement of E  with respect to bulk materials has been obtained by con"ning electron and hole wave functions in nanostructures of low dimen- sionality (quantum con"nement), the most promis- ing type of structures being quasi-one-dimensional systems (quantum wires); within GaAs-based * Corresponding author. Tel.: #39-059-586072; fax: #39- 059-367488. E-mail address: goldoni@unimo.it (G. Goldoni) materials, however, the observed values of E  are still well below the room-temperature thermal energy. In this paper we review an alternative strategy recently proposed [1] to enhance E  : it combines quantum con"nement with remote dielectric con- "nement. As "rst pointed out by Keldysh [2], the electron}hole Coulomb attraction can be greatly enhanced in layered structures with strong di- electric mismatch, due to the polarization charge induced at the interfaces. For conventional semiconductor nanostructures such as GaAs/ AlGaAs- or GaAs/InGaAs-based samples, how- ever, this is a minor e!ect due to the small dielectric mismatch between the constituents [3]. On the other hand, interfaces between III}V semiconduc- tors and materials with very low dielectric con- stants, such as oxides or vacuum, are usually very 0921-4526/99/$ - see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 0 4 3 0 - 5