Physica B 340–342 (2003) 1082–1085 Strain release in InGaAs/In x Al 1x As/InP heterostructures O. Yastrubchak a , J. Bak-Misiuk a, *, E. Lusakowska a , J. Kaniewski b , J.Z. Domagala a , T. Wosi ! nski a , A. Shalimov a , K. Regi ! nski b , A. Kudla b a Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland b Institute of Electron Technology, 02-668 Warsaw, Poland Abstract Two micrometer thick In 0.53 Al 0.47 As and In 0.50 Al 0.50 As layers covered by 10 nm thick In 0.53 Ga 0.47 As cap layers were grown on the (0 0 1) oriented InP substrates by molecular beam epitaxy. The structures were investigated using high- resolution X-ray diffractometry, spectroscopic ellipsometry and atomic force microscopy (AFM). Strain release in the In 0.53 Al 0.47 As layer was almost symmetrical. Contrary to this the lateral strain in the In 0.50 Al 0.50 As layer was found to be different along the [1 1 0] and ½ % 110 crystallographic directions. The anisotropy of surface morphology for the both kinds of samples was observed in AFM image. The surface undulation was accompanied with the microcracks formation in the cap layer. r 2003 Elsevier B.V. All rights reserved. PACS: 68.35.Gy; 68.55.Jk; 61.72.Lk Keywords: Semiconductor heterostructures; Strain relaxation; Misfit dislocations 1. Introduction In-based layers are of high technological interest due to their applications in optical telecommuni- cation, computing as well as quantum electronics. However, lattice parameters of epitaxial layers and substrates are often different and therefore strain is created. Recently, considerable research activity has been devoted to study the mechanism of strain relaxation [1–8]. Despite progress, the problem seems to be far from being completely understood [2,3]. Anisotropic relaxation in III–V layer can be accompanied by creation of misfit dislocations with various densities along [1 1 0] and ½ % 110 directions [4]. Anisotropic relaxation for tensile strained In x Ga 1x As/InP (0.2oxo0.36) was re- ported [5]. It is well known that the lattice parameter of In x Al 1x As, x ¼ 0:52 layer is fully matched to the InP substrate. Therefore, by suitable changes of the x-value one can obtain partially tensile strained (In x Al 1x As, xo0:52) or partially com- pressive strained (In x Al 1x As, x > 0:52) layers on InP. In the present paper, In x Al 1x As layers under tensile strain (x ¼ 0:50) and compressive strain (x ¼ 0:53) have been studied. 2. Experimental Two micrometer thick In 0.50 Al 0.50 As/InP and In 0.53 Al 0.47 As layers, covered by 10 nm thick ARTICLE IN PRESS *Corresponding author. Tel.: +48-22-8436-034; fax: +48- 22-8430-926. E-mail address: bakmi@ifpan.edu.pl (J. Bak-Misiuk). 0921-4526/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2003.09.183