Materials Science and Engineering B69 – 70 (2000) 261 – 265 Annealing experiments on supercritical Si 1– x Ge x layers grown by RPCVD K. Grimm a,b, *, L. Vescan a , C.C.G. Visser b , L.K. Nanver b , H. Lu ¨th a a Institut fu ¨r Schicht - und Ionentechnik, Forschungszentrum Ju ¨lich GmbH, D-52425 Ju ¨lich, Germany b Laboratory of ECTM, DIMES, TU Delft, Feldmannweg 17, 2628 CB Delft, The Netherlands Abstract This paper presents a study of the relaxation mechanisms for SiGe epitaxy performed by reduced pressure chemical vapor deposition (RPCVD) in a commercially available single wafer epitaxial reactor. The samples were grown at 500°C and an overall pressure of 40 Torr, with SiH 2 Cl 2 and GeH 4 as precursor gasses. In contrast to the situation for molecular beam epitaxy (MBE), we found that under RPCVD conditions the relaxation by 3D-growth was strongly suppressed. Relaxation then occurred by the development of misfit dislocations even in the case of high Ge-concentrations ( 40%). This behavior is attributed to the high hydrogen coverage of the substrate surface during the RPCVD, which reduces the surface migration of the adsorbed species. Furthermore, the relaxation mechanism has been studied in annealing experiments where wave and island formation was observed. The annealing experiments clearly confirm that surface migration plays a significant role for 3D-growth. Using the annealing procedure layers of high island density and strong photoluminescence have been produced. © 2000 Elsevier Science S.A. All rights reserved. Keywords: Chemical vapor deposition; SiGe islands; Annealing; Surfactant; Photoluminescence; LEDs www.elsevier.com/locate/mseb 1. Introduction The epitaxy of SiGe by CVD has proven itself in the industrial production of semiconductor devices, in par- ticular SiGe heterobipolar transistors (HBTs). These devices are often designed to the limits of the critical Ge concentration and layer thickness. Also in optoelectron- ics, both SiGe with high Ge concentration and relaxed SiGe are being investigated for use in a variety of applications such as detectors and waveguides. Knowl- edge of the growth kinetics of these layers is very important for understanding and controlling the relax- ation mechanism. In the case of MBE, these aspects have been very extensively studied and are to some extent understood [2,3], but the mechanisms which govern the epitaxial growth of CVD material are at present not so well known. The need for investigations in this field has increased in recent years since low temperature CVD is becoming a production ripe tech- nique that offers new possibilities of growing thick layers with high Ge concentrations. Investigations on elastic strain relaxation are particularly of interest since some degree of control of the production of SiGe islands seems feasible. Such SiGe island structures are interesting candidates for the fabrication of tunneling diodes and light emitting diodes [1,11]. 2. Experimental procedures The investigated Si 1 -x Ge x layers were grown on Si(001) wafers in an ASM Epsilon 1 CVD-reactor using dichlorosilane and germane as precursors and hydrogen as carrier gas. The native oxide of the wafers was removed in situ by thermal desorption at 1150°C. Be- fore the deposition of the Si 1 -x Ge x layer a Si buffer layer with a nominal thickness of 1 m was grown. The deposition of the Si 1 -x Ge x -layer was carried out under a total pressure of 40 Torr and at growth temperatures around 500°C. The anneal procedure was performed in situ directly after growth at varying temperatures (600 – 1000°C) in ambient hydrogen. Growth rates and germanium concentrations of the layers have been evaluated by RBS-measurements using 2 MeV He + -ions as scattering particles. Transmission * Corresponding author. E-mail address: k.grimm@fz-juelich.de (K. Grimm) 0921-5107/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved. PII:S0921-5107(99)00305-0