Journal of Alloys and Compounds 362 (2004) 254–260 Pressure-induced defect structure changes in thin AlGaAs layers J. Bak-Misiuk a,∗ , A. Shalimov a , W. Paszkowicz a , A. Misiuk b , J. Härtwig c , J. Adamczewska a , J. Trela a , J.Z. Domagala a , D. Dobosz a , Z.R. Zytkiewicz a a Institute of Physics, PAS, Al. Lotnikow 32/46, 02-668 Warsaw, Poland b Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland c European Synchrotron Radiation Facility, F-38043 Grenoble, France Received 17 June 2002; received in revised form 8 January 2003; accepted 15 February 2003 Abstract A study of the defect structure of Al x Ga 1-x As/GaAs layers with varied primary strain state prepared by LPE method and subsequently annealed under high uniform pressure is reported. An influence of high hydrostatic pressure–high temperature (1.2 GPa and 920 K or 1070 K applied for 1 h) on the strain state and defect structure of the layers was investigated by high-resolution X-ray diffractometry and topography (the latter done at the ID19 beamline, ESRF). A treatment-induced change of defect structure was detected for all samples, being more pronounced for the case of treatment at 1070 K. The appearance of treatment-induced stresses at the precipitate/matrix boundary caused the creation of new defects and resulted in an increase of rocking curve width and in enhancement of the diffuse scattering intensity. © 2003 Elsevier B.V. All rights reserved. Keywords: Semiconductors; Precipitation; X-ray diffraction; Strain; High pressure; Synchrotron radiation 1. Introduction Annealing of semiconductor heterostructures under en- hanced hydrostatic pressure of ambient gas (HP–HT treat- ment) can result in changed strain state. This effect has been reported for various materials grown by molecular beam epi- taxy (MBE): the fully strained AlGaAs/GaAs samples [1–3], relaxed InAs/InP and GaAs/Si systems [4,5], as well as for strained or partially relaxed InGaAs/GaAs samples [6]. On the contrary, strain changes have not been detected either for the InGaAs/GaAs [7] or for ZnTe/GaAs [4] layers grown by the MOCVD method. An effect of the HP–HT treatment is that some additional defects can nucleate and grow on the existing primary structural irregularities [8]. The influence of high pressure on the strain state and defect structure of AlGaAs/GaAs system has been reported earlier only for AlGaAs layers grown by MBE method [1–3]. The goal of the present work is the determination of the influence of high hydrostatic pressure and high temperature on the strain state and defect structure of the liquid phase ∗ Corresponding author. Tel.: +48-22-8436-034; fax: +48-22-8430-926. E-mail address: bakmi@ifpan.edu.pl (J. Bak-Misiuk). epitaxy (LPE)-grown AlGaAs/GaAs heteroepitaxial layers which exhibit different initial strain state. 2. Experimental The Al x Ga 1-x As layers with varying Al content were grown on the (001) oriented GaAs substrates by the LPE method at T = 1070 K. The primary strain state and defect structure of the layers were varied through: i) the layer com- position, x (0.3<x<0.75) and ii) the layer thickness, t (0.4 m<t<4.5 m). The layer thickness was determined opti- cally by inspection of the sample cross-section. The features of the studied samples are listed in Table 1. The aluminium content was determined by secondary ion mass spectrom- etry (SIMS) as well as calculated from the relaxed lattice parameter value, assuming the validity of the Vegard’s rule. The relaxed lattice parameter, a relax , of the layer material was calculated from the equation: a relax = (a ⊥ + 2a || )/(1 + 2C) (1) where a ⊥ means the out-of-plane lattice parameter; a || is the in-plane lattice parameter; C = (1 - ν)/(1 + ν); and ν is the Poisson ratio (linear relation between ν AlAs = 0.275 0925-8388/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0925-8388(03)00594-2