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Title: Thermal stability and relaxation mechanisms in compressively strained Ge{sub 0.94}Sn{sub 0.06} thin films grown by molecular beam epitaxy

Abstract

Strained Ge{sub 1-x}Sn{sub x} thin films have recently attracted a lot of attention as promising high mobility or light emitting materials for future micro- and optoelectronic devices. While they can be grown nowadays with high crystal quality, the mechanism by which strain energy is relieved upon thermal treatments remains speculative. To this end, we investigated the evolution (and the interplay) of composition, strain, and morphology of strained Ge{sub 0.94}Sn{sub 0.06} films with temperature. We observed a diffusion-driven formation of Sn-enriched islands (and their self-organization) as well as surface depressions (pits), resulting in phase separation and (local) reduction in strain energy, respectively. Remarkably, these compositional and morphological instabilities were found to be the dominating mechanisms to relieve energy, implying that the relaxation via misfit generation and propagation is not intrinsic to compressively strained Ge{sub 0.94}Sn{sub 0.06} films grown by molecular beam epitaxy.

Authors:
; ; ;  [1];  [2]; ; ;  [3];  [1];  [2];  [4]; ;  [5];  [6];  [7]; ;  [1]
  1. Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium)
  2. (Belgium)
  3. Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin (Germany)
  4. (Germany)
  5. imec, Kapeldreef 75, 3001 Leuven (Belgium)
  6. Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)
  7. Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba West SCR, 16-1 Onogawa, Tsukuba, Ibaraki 305-8569 (Japan)
Publication Date:
OSTI Identifier:
22598843
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTALS; DIFFUSION; GERMANIUM; HEAT TREATMENTS; INSTABILITY; MOLECULAR BEAM EPITAXY; MORPHOLOGY; OPTOELECTRONIC DEVICES; RELAXATION; SPECTROSCOPY; STABILITY; STRAINS; SURFACES; THIN FILMS; TIN

Citation Formats

Fleischmann, C., Lieten, R. R., Shimura, Y., Vandervorst, W., imec, Kapeldreef 75, 3001 Leuven, Hermann, P., Hönicke, P., Beckhoff, B., Seidel, F., imec, Kapeldreef 75, 3001 Leuven, Institut für Elektronik-und Sensormaterialien, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 3, 09599 Freiberg, Richard, O., Bender, H., Zaima, S., Uchida, N., Temst, K., and Vantomme, A.. Thermal stability and relaxation mechanisms in compressively strained Ge{sub 0.94}Sn{sub 0.06} thin films grown by molecular beam epitaxy. United States: N. p., 2016. Web. doi:10.1063/1.4961396.
Fleischmann, C., Lieten, R. R., Shimura, Y., Vandervorst, W., imec, Kapeldreef 75, 3001 Leuven, Hermann, P., Hönicke, P., Beckhoff, B., Seidel, F., imec, Kapeldreef 75, 3001 Leuven, Institut für Elektronik-und Sensormaterialien, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 3, 09599 Freiberg, Richard, O., Bender, H., Zaima, S., Uchida, N., Temst, K., & Vantomme, A.. Thermal stability and relaxation mechanisms in compressively strained Ge{sub 0.94}Sn{sub 0.06} thin films grown by molecular beam epitaxy. United States. doi:10.1063/1.4961396.
Fleischmann, C., Lieten, R. R., Shimura, Y., Vandervorst, W., imec, Kapeldreef 75, 3001 Leuven, Hermann, P., Hönicke, P., Beckhoff, B., Seidel, F., imec, Kapeldreef 75, 3001 Leuven, Institut für Elektronik-und Sensormaterialien, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 3, 09599 Freiberg, Richard, O., Bender, H., Zaima, S., Uchida, N., Temst, K., and Vantomme, A.. Sun . "Thermal stability and relaxation mechanisms in compressively strained Ge{sub 0.94}Sn{sub 0.06} thin films grown by molecular beam epitaxy". United States. doi:10.1063/1.4961396.
@article{osti_22598843,
title = {Thermal stability and relaxation mechanisms in compressively strained Ge{sub 0.94}Sn{sub 0.06} thin films grown by molecular beam epitaxy},
author = {Fleischmann, C. and Lieten, R. R. and Shimura, Y. and Vandervorst, W. and imec, Kapeldreef 75, 3001 Leuven and Hermann, P. and Hönicke, P. and Beckhoff, B. and Seidel, F. and imec, Kapeldreef 75, 3001 Leuven and Institut für Elektronik-und Sensormaterialien, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 3, 09599 Freiberg and Richard, O. and Bender, H. and Zaima, S. and Uchida, N. and Temst, K. and Vantomme, A.},
abstractNote = {Strained Ge{sub 1-x}Sn{sub x} thin films have recently attracted a lot of attention as promising high mobility or light emitting materials for future micro- and optoelectronic devices. While they can be grown nowadays with high crystal quality, the mechanism by which strain energy is relieved upon thermal treatments remains speculative. To this end, we investigated the evolution (and the interplay) of composition, strain, and morphology of strained Ge{sub 0.94}Sn{sub 0.06} films with temperature. We observed a diffusion-driven formation of Sn-enriched islands (and their self-organization) as well as surface depressions (pits), resulting in phase separation and (local) reduction in strain energy, respectively. Remarkably, these compositional and morphological instabilities were found to be the dominating mechanisms to relieve energy, implying that the relaxation via misfit generation and propagation is not intrinsic to compressively strained Ge{sub 0.94}Sn{sub 0.06} films grown by molecular beam epitaxy.},
doi = {10.1063/1.4961396},
journal = {Journal of Applied Physics},
number = 8,
volume = 120,
place = {United States},
year = {Sun Aug 28 00:00:00 EDT 2016},
month = {Sun Aug 28 00:00:00 EDT 2016}
}
  • In this letter, we study the structural and magnetic properties of Ge{sub 1-x-y}Sn{sub x}Mn{sub y} films grown on Ge(001) by low temperature molecular beam epitaxy using X-ray diffraction, high resolution transmission electron microscopy, and superconducting quantum interference device. Like in Mn doped Ge films, Mn atoms diffuse during the growth and aggregate into vertically aligned Mn-rich nanocolumns of a few nanometers in diameter. Transmission electron microscopy observations in plane view clearly indicate that the Sn incorporation is not uniform with concentration in Mn rich vertical nanocolumns lower than the detection limit of electron energy loss spectroscopy. The matrix exhibits amore » GeSn solid solution while there is a Sn-rich GeSn shell around GeMn nanocolumns. The magnetization in Ge{sub 1-x-y}Sn{sub x}Mn{sub y} layers is higher than in Ge{sub 1-x}Mn{sub x} films. This magnetic moment enhancement in Ge{sub 1-x-y}Sn{sub x}Mn{sub y} is probably related to the modification of the electronic structure of Mn atoms in the nanocolumns by the Sn-rich shell, which is formed around the nanocolumns.« less
  • We theoretically investigate germanium-tin alloy as a semiconductor for the design of near infrared optical modulators in which the Ge{sub 1−x}Sn{sub x} alloy is the active region. We have calculated the electronic band parameters for heterointerfaces between strained Ge{sub 1−x}Sn{sub x} and relaxed Si{sub 1−y}Ge{sub y}. Then, a type-I strain-compensated Si{sub 0.10}Ge{sub 0.90}/Si{sub 0.16}Ge{sub 0.84}/Ge{sub 0.94}Sn{sub 0.06} quantum well heterostructure optimized in terms of compositions and thicknesses is studied by solving Schrödinger equation without and under applied bias voltage. The strong absorption coefficient (>1.5 × 10{sup 4} cm{sup −1}) and the shift of the direct transition under large Stark effect at 3 V aremore » useful characteristics for the design of optoelectronic devices based on compressively strained IV-IV heterostructures at near infrared wavelengths.« less
  • We investigated the critical thickness (h{sub c}) for plastic relaxation of Ge{sub 1−x}Sn{sub x} grown by molecular beam epitaxy. Ge{sub 1−x}Sn{sub x} films with various Sn mole fraction x (x ≤ 0.17) and different thicknesses were grown on Ge(001). The strain relaxation of Ge{sub 1−x}Sn{sub x} films and the h{sub c} were investigated by high-resolution x-ray diffraction and reciprocal space mapping. It demonstrates that the measured h{sub c} values of Ge{sub 1−x}Sn{sub x} layers are as much as an order of magnitude larger than that predicted by the Matthews and Blakeslee (M-B) model. The People and Bean (P-B) model was also usedmore » to predict the h{sub c} values in Ge{sub 1−x}Sn{sub x}/Ge system. The measured h{sub c} values for various Sn content follow the trend, but slightly larger than that predicted by the P-B model.« less
  • The authors report the far-infrared measurements of the electron cyclotron resonance absorption in n-type Si/Si{sub 0.62}Ge{sub 0.38} and Si{sub 0.94}Ge{sub 0.06}/Si{sub 0.62}Ge{sub 0.38} modulation-doped heterostructures grown by rapid thermal chemical vapor deposition. The strained Si and Si{sub 0.94}Ge{sub 0.06} channels were grown on relaxed Si{sub 0.62}Ge{sub 0.38} buffer layers, which consist of 0.6 {micro}m uniform Si{sub 0.62}Ge{sub 0.38} layers and 0.5 {micro}m compositionally graded relaxed SiGe layers from 0% Ge to 38% Ge. The buffer layers were annealed at 800 C for 1 hr to obtain complete relaxation. The sampled had 100 {angstrom} spacers and 300 {angstrom} 2 {times} 10{supmore » 19} cm{sup {minus}3} n-type supply layers on the tops of the 75 {angstrom} channels. The far-infrared measurements of electron cyclotron resonance were performed at 4K with the magnetic field of 4--8 Tesla. The effective masses determined from the slope of center frequency of absorption peak vs applied magnetic field plot are 0.20 m{sub o} and 0.19 m{sub o} for the two dimensional electron gases in the Si and Si{sub 0.94}Ge{sub 0.06} channels, respectively. The Si effective mass is very close to that of two dimensional electron gas in Si MOSFET (0.198m{sub o}). The electron effective mass of Si{sub 0.94}Ge{sub 0.06} is reported for the first time and about 5% lower than that of pure Si.« less
  • A double-low-temperature-buffer variable-temperature growth scheme was studied for fabrication of strain-relaxed thin Si{sub 0.6}Ge{sub 0.4} layer on Si(001) by using molecular beam epitaxy (MBE), with particular focuses on the influence of growth temperature of individual low-temperature-buffer layers on the relaxation process and final structural qualities. The low-temperature buffers consisted of a 40 nm Si layer grown at an optimized temperature of {approx}400 deg. C, followed by a 20 nm Si{sub 0.6}Ge{sub 0.4} layer grown at temperatures ranging from 50 to 550 deg. C. A significant relaxation increase together with a surface roughness decrease both by a factor of {approx}2, accompaniedmore » with the cross-hatch/cross-hatch-free surface morphology transition, took place for the sample containing a low-temperature Si{sub 0.6}Ge{sub 0.4} layer that was grown at {approx}200 deg. C. This dramatic change was explained by the association with a certain onset stage of the ordered/disordered growth transition during the low-temperature MBE, where the high density of misfit dislocation segments generated near surface cusps largely facilitated the strain relaxation of the top Si{sub 0.6}Ge{sub 0.4} layer.« less