Evaluation of Anisotropic Three-Dimensional Strain Relaxation in Stripe-Shaped Ge_1-xSn_x Mesa Structure

Abstract

We evaluated the anisotropic three-dimensional strain relaxation in the patterned Ge1-xSnx mesa structure by Raman spectroscopy and X-ray diffraction(XRD). The strain states in the channel region change complicatedly depending on the channel shape. Therefore, accurate strain evaluation technique is strongly desired. In this study, measurements were carried out using a thin Ge1-xSnx film grown epitaxially on a Ge substrate by metal organic chemical vapor deposition (MOCVD). After growing the epitaxial film, a stripe-shaped mesa structures simulating the channel shape were fabricated. From the results of Raman spectroscopy and XRD, strain relaxation was confirmed at pattern width W = 0.2 μm or less in the in-plane minor axis and the out-of-plane direction.

Evaluation of Thermal Expansion Coefficient in Ge1-x Sn x Nanowire Using Reciprocal Space Mapping

“…indicates that the nanowires had larger lattice spacing than the Ge0.968Sn0.032 blanket film, and in-plane compressive strain is relaxed in the nanowires, as previously reported [11,16]. The lattice parameters of Ge0.…”

“…The Ge1−xSnx thin films were epitaxially grown on Ge (001) substrate with thicknesses of 34 and 45 nm by home-made metal organic chemical vapor deposition [11,13]. Sn concentration of Ge1−xSnx was 3.2% confirmed by Rutherford backscattering spectroscopy [11,13]. Then, the Ge0.968Sn0.032 nanowires were fabricated by electron beam lithography and dry etching.…”

“…In general, in-plane compressive strain is induced in epitaxially grown Ge1−xSnx thin film on Ge substrate due to the difference in lattice parameters (Ge1−xSnx thin film and Ge substrate). We have previously reported that anisotropic strain relaxation occurs in the Ge 1−x Sn x nanowires by oil-immersion Raman spectroscopy and synchrotron radiation X-ray diffraction (XRD) measurement [11,12]. Anisotropic strain relaxation may cause the change for not only carrier mobility (electrical characteristics) but also thermal expansion [9], which should affect Seebeck coefficient and thermal conductivity.…”

Strain distributions in carbon-doped silicon nanowires along [110] and [100] investigated by X-ray diffraction

“…These nanowires were patterned with periodicities of 5 μm and 15 μm in the shortand long-side directions in square areas of 1.5 mm × 1.5 mm. [32][33][34] As-deposited areas of C-doped Si thin films were retained as references.…”

“…5,6,18,22) These methods give excellent results with very fine spatial resolution but are not suitable for statistical investigations since local and individual characteristics are emphasized By observing samples with many nanowires periodically arranged within a 1.5 mm × 1.5 mm region with X-rays of sub-millimeter beam width, we obtained statistically averaged characteristics while eliminating the effects of individual nanowire differences, as previously reported. [32][33][34] Previously, we found an indication that [100] nanowires were more relaxed than [110] nanowires by assuming that all nanowires have uniform lattice spacings. 34) However, differences between [100] and [110] C-doped Si nanowires were very ambiguous, since spreading RSM profiles in the observations indicate quite large distributions of lattice spacings.…”