Damage behaviour of GaAs/AlAs multilayer structures S. Magalha ˜es a , A. Fonseca a , N. Franco a , N.P. Barradas a,b , N. Sobolev c , R. Hey d , H. Grahn d , E. Alves a,b, * a Departamento de Fisica, Instituto Tecnolo ´ gico e Nuclear, EN 10, 2686-953 Sacave ´m, Portugal b Centro de Fı ´sica Nuclear da Univ. de Lisboa, Av. Gama Pinto 2, 1649-003 Lisboa, Portugal c Departamento de Fı ´sica, Univ. de Aveiro, 3810-193 Aveiro, Portugal d Paul Drude Institute of Solid State Electronics, 10117 Berlin, Germany Available online 19 May 2006 Abstract In this work, we studied the implantation damage formation into GaAs/AlAs multilayers with different periods. The superlattices (S i ) were implanted with 150 keV Ar + ions at 77 K with fluences in the range (1–10) · 10 13 cm 2 . The samples were studied with Rutherford backscattering (RBS)/channeling and X-ray diffraction techniques and it was found that, even for the thicker GaAs (68 nm)/AlAs (82 nm) period, the higher fluence (10 14 cm 2 ) were not enough to amorphize the implanted region. Since the same fluence renders pure GaAs amorphous this is a clear evidence for the influence of the multistructure nature of the samples on the damage production. The X-ray results reveal a new peak shifted to lower angles indicating the formation of a region with higher lattice parameters. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Implantation damage; Superlattices; Amorphization 1. Introduction Superlattices are a class of epitaxial growth structures achieved by periodic depth modulation of the composition. So far the GaAs/AlAs structure is one the most studied sys- tems [1]. The importance of this low dimensional structure for development of new optoelectronic devices is behind the motivation of these studies. Since crystalline quality is one of the crucial factors influencing the behaviour of the structures, several works were focused on those issues [2– 6]. Moreover the use of ion implantation to change proper- ties of semiconductors (structural, optical and electrical properties) is a well established technique which introduces a large amount of damage in the structure. Previous studies indicate a strong influence of the interfaces on the damage formation even for high implantation energy (maximum 2.7 MeV) and showed the importance of mixing at the interfaces on the amorphization process [2,3]. Although amorphization processes are well established in bulk crystals [7], less is known for more complex struc- tures such as multilayer systems, where interface phenom- ena and strain must be taken into consideration. It was found that these parameters play a major role in the amor- phization development [2,6,8]. Despite all the research work done there are several aspects underlying the damage production in multi-quantum well structures which must be clarified. In this work, we studied the implantation damage formation in GaAs/AlAs superlattices with different thicknesses. We used Rutherford backscattering/channel- ing and X-ray diffraction techniques to study the implanted samples. Our results indicated a limited influence of interface mixing on the damage behaviour in the fluence range studied. 0168-583X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.03.157 * Corresponding author. Address: Instituto Tecnolo ´ gico e Nuclear, EN 10, 2686-953 Sacave ´m, Portugal. Tel.: +351 21 9946086; fax: +351 21 9941525. E-mail address: ealves@itn.pt (E. Alves). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 249 (2006) 890–893 NIM B Beam Interactions with Materials & Atoms