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Transmission electron microscopy of misfit dislocation and strain relaxation in lattice mismatched III-V heterostructures versus substrate surface treatment Y. Wang,1 P. Ruterana,1 L. Desplanque,2 S. El Kazzi,2 and X. Wallart2 1

CIMAP UMR 6252 CNRS-ENSICAEN-CEA-UCBN, 6, Boulevard du Maréchal Juin, 14050 Caen Cedex, France 2 Institut d’Electronique, de Microélectronique et de Nanotechnologie, UMR-CNRS 8520, BP 60069, 59652 Villeneuve d’Ascq Cedex, France ABSTRACT High resolution transmission electron microscopy in combination with geometric phase analysis is used to investigate the interface misfit dislocations, strain relaxation, and dislocation core behavior versus the surface treatment of the GaAs for the heteroepitaxial growth of GaSb. It is pointed out that Sb-rich growth initiation promotes the formation of a high quality network of Lomer misfit dislocations that are more efficient for strain relaxation. INTRODUCTION In the last decade, growth of antimony-based III-V semiconductors have been attracting much attention for potential applications in high-speed and low-power electronic and optoelectronic devices, due to their wide range bandgaps, small electron effective mass and high electron mobility [1-3]. Unfortunately, the strain and high density of defects due to the large mismatch between the III-Sb epitaxial layers and substrate (e.g. GaAs, GaP, Si) has until have an obstacle for both the electrical and optical properties of the devices. Because of the large mismatch (7.8%, in the case of GaSb/GaAs), the critical thickness is expected to be within the range of few monolayers (MLs) and subsequently the misfit dislocations are generated at the interface to release the misfit strain. The growth processes of hetero-structures have been largely investigated, and both 90o Lomer and 60o misfit dislocation were reported form at the interface [4-6]. For the epitaxial growth of semiconductor, it is known that the surface treatment plays a critical role in the growth process (growth model, surface morphology, stoichiometry …) of the epitaxial layer [7]. In the present work we report on a study by means of conventional TEM and highresolution TEM (HRTEM) combined with geometric phase analysis method (GPA) on the interface misfit dislocations and strain relief in the GaSb epitaxial grown on (001) GaAs with Ga-rich or Sb-rich surface treatment. This report is focused on the possible effects of the surface treatment of (001) GaAs on the arrangement of the interface misfit dislocations and strain relaxation. EXPERIMENT The investigated GaSb layers were grown on GaAs (001) ±0.5o semi-insulating substrates by Molecular Beam Epitaxy in a 3-inch Riber Compact 21TM reactor with a base pressure better

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than 1×10-10 Torr. After de-oxidation at 625°C under an As flux, a 500 nm GaAs layer was first grown at 580°C to smooth the surface. Then the As valve was closed and the sample temperature was decreased to 510°C under Sb2 flux for sample B and without any flux for sample A. For sample A, 1 ML Ga was deposited just before gro