J&3 *H __ . zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA __ I!3 NIUMI B . Beam Inteactions with Materials 8 Atoms ELSEVIER Nuclear Instruments and Methods in Physics Research B 136-138 ( 1998) 1062 ~1067 Ion bombardment induced relaxation of strained AlGaAs/GaAs heterostructures studied by the complementary use of RBS- channeling and X-ray synchrotron radiation A. Turos a-b-* , W. Wierzchowski ‘, K. Wieteska ‘, E. Wendler ‘, W. Wesch d, W. Graeff e, R. Griitzschel ‘, W. Strupiliski a Abstract AI,Gai_,As epitaxial layers grown on semi-insulating GaAs (SI-GaAs) substrates with .Y = 0.15 and on in-doped GaAs with s = 0.45 were implanted at room temperature with 1.5 MeV Se ions to fluences ranging from 0.6 x IO” to 4 x 10IJ at/cm’. Implanted crystals were analyzed with 1.8 MeV JHe ions using the RBS/channeling technique. In order to determine the defect structure and their depth profiles measurements were carried out at two different temper- atures: 295 and 105 K. XRD with synchrotron beams was used for structural analysis. White beam topography was used to detect lattice deformation and strain relaxation. The lattice parameters were determined by rocking curve mea- surements with a monochromatic beam. For all samples a significant tetragonalization of the implanted region was ob- served. For the layers grown on SI-GaAs the lattice distortion increases with increasing ion dose until a critical lattice strain is attained. At that point the complete relaxation of the epitaxial layer occurs. In contrast, no relaxation was ob- served for layers grown on practically defect free in-doped substrates. The mechanism of this transformation is attrib- uted to the much higher dislocation density in the SI-GaAs substrate. Nucleation of new dislocations at defects produced by ion implantation and their interaction with threading dislocations leads to the strain relaxation by plastic deformation of epitaxial layers. 0 1998 Elsevier Science B.V. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Kqwords: Epitaxial layers; Ion bombardment: RBS/channeling: XRD 1. Introduction *Corresponding author. Address: Institute of Electronic Materials Technology. ul. Wolczynska 133. 0 I-91 9 Warsaw. Poland. Tel.: ++48-22.394003; fax: ++48-39120764; e-mail: turos@fuw.edu.pl. AlGaAs has attracted considerable attention for designing and fabricating new electronic and optoelectronic devices. Because of the small lattice 0168-583X/98/$19.00 0 1998 Elsevier Science B.V. All rights reserved. PfISO168-583X(97)00802-1