Raman study of strain relaxation in Ge on Si

Ichimura, M.; Usami, Akira; Wakahara, Akihiro; Sasaki, Akio

doi:10.1063/1.359258

Cited by 14 publications

(10 citation statements)

References 16 publications

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“…3b to be dependent on d. The value of W R for a Ge wafer is indicated by the red tick mark on the y-axis. The value of W R for the Ge film was 8.4 cm −1 at d = 10 nm; it decreased sharply with increasing d for 10 nm < d < 50 nm because of phonon confinement, [25][26][27] whereas the decrease became more gradual with for d > 50 nm because of improving crystallinity. At d > 100 nm, W R was asymptotically close to that of bulk Ge (4.05 cm −1 ).…”

Section: Resultsmentioning

confidence: 95%

Sputter Epitaxial Growth of Flat Germanium Film with Low Threading-Dislocation Density on Silicon (001)

Yeh

Matsumoto

Sugihara

et al. 2014

ECS J. Solid State Sci. Technol.

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Fast epitaxy of Ge on Si(001) was realized by DC sputtering at 2.1 nm · s −1 and 360 • C; the resulting film was optically flat without a cross-hatch structure. After annealing at 700 • C, 90 • -full-edge dislocations dominated the Ge-Si interface and the threadingdislocation density (TDD) of the Ge film was below 10 4 cm −2 , which is three orders of magnitude lower than the value of Ge films prepared by other methods. The extremely low TDD might be attributable to the spaces vacated by desorbed Ar within the film that served as dislocation sinks during sputtering. Acceptor-band conduction, which was at 0.02 eV above the valence band and was induced by dislocations, was observed with a hole mobility of 3-10 cm 2 · V −1 · s −1 in the film prepared without annealing. After annealing at 700 • C, the ionized-defect scattering in the film was considerably decreased and a mobility of 1180 cm 2 · V −1 · s −1 was obtained. The direct band gap energy of the film prepared without annealing was 0.81 eV, and became 0.79 eV after annealing.

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Section: Resultsmentioning

confidence: 95%

Sputter Epitaxial Growth of Flat Germanium Film with Low Threading-Dislocation Density on Silicon (001)

Yeh

Matsumoto

Sugihara

et al. 2014

ECS J. Solid State Sci. Technol.

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“…The SbϪGe phonon is removed through exposure to air, confirming that it was a surface feature. It should be noted that despite the existence of many Raman studies of this system, [33][34][35][36][37] this data represent an observation of surface related phonons involving Sb at 130.5 cm Ϫ1 ͑for SbϪSi ) ͑see also Ref. 29͒ and 141 cm Ϫ1 ͑for SbϪGe ).…”

Section: Surface Phonons: Establishing a Growth Model For Smg On Vicimentioning

confidence: 76%

“…All previous Raman studies have been carried out in air, after the surfactant had been removed and a thick Si layer grown to protect the Ge layer. [33][34][35][36][37] By following the intensity of the SbϪSi and SbϪGe surface phonons with Ge coverage, interesting information concerning SMG on vicinal Si͑001͒ is revealed ͑see Fig. 5͒.…”

Section: Surface Phonons: Establishing a Growth Model For Smg On Vicimentioning

confidence: 99%

Sb-mediated Ge growth on singular and vicinal Si(001) surfaces: A surface optical characterization study

et al. 2000

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In this work, we apply Raman spectroscopy ͑RS͒ and spectroscopic ellipsometry ͑SE͒ to surfactant mediated growth ͑SMG͒ of Ge on Si͑001͒ surfaces. Under molecular-beam epitaxy conditions, a growth temperature of 400°C and in the absence of a predeposited surfactant ͑Sb͒ monolayer, we show that SE can be used to determine the Stranski-Krastanov critical thickness for island formation. In the presence of a predeposited Sb monolayer, SE predicts that layer-by-layer growth is possible up to a Ge coverage of 20 monolayers ͑MLs͒. However, no evidence of relaxation through dislocation formation, known to exist in this coverage regime, could be detected. With RS, we present one of the first studies of Sb mediated growth on a vicinal Si͑001͒ substrate. Two Sb surface related phonon peaks are identified, one associated with Sb dimers bonded to the Si͑001͒ substrate (130.5 cm Ϫ1 ), the other with Sb dimers on the grown Ge epilayer (141 cm Ϫ1 ). The former disappears and the latter appears gradually with increased Ge coverage up to 3.5 MLs. This indicates that surfactant exchange occurs differently on vicinal Si͑001͒ than on singular Si͑001͒, where exchange has been shown to be complete by deposition of between 0.5-1.0 monolayer ͑ML͒. To explain this difference, step bunching must occur during the initial stages of growth on vicinal Si ͑001͒, leading to areas of preferred growth on the surface. At a higher Ge coverage of 20 MLs, theoretical predictions of the Raman shift for a strained pseudomorphically grown Ge layer show good agreement with the Raman data presented. This demonstrates that even at 20 ML coverage, some areas of unrelaxed Ge must still exist, pointing to inhomogeneities within the Ge epilayer, as predicted by our model for SMG on a step bunched Si͑001͒ substrate.

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“…The peak position shifts under the presence of strain/stress and isotopic variations. 4,5,9,[27][28][29][30][31] Alloys of Si and Ge (Si 1-x Ge x ) typically show three Raman peaks of Ge-Ge (∼300 cm −1 ), Si-Ge (∼400 cm −1 ) and Si-Si (∼500 cm −1 ). The position and intensity of the three peaks depends on the composition of the alloys.…”

Section: Resultsmentioning

confidence: 99%

“…Relatively high surface roughness makes process integration difficult. [3][4][5][6] For planarization of Ge heteroepitaxial layers, chemical mechanical polishing (CMP) was also studied. 7,8 For optoelectric device applications, Ge-on-insulator (GeOI) wafer fabrication techniques have been studied.…”

mentioning

confidence: 99%

Characterization of Hetero-Epitaxial Ge Films on Si Using Multiwavelength Micro-Raman Spectroscopy

Yoo¹,

Kang²,

Ueda³

et al. 2014

ECS J. Solid State Sci. Technol.

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To meet various physical property requirements of materials for advanced applications for specific devices, combinations of Si/Ge, Ge/Si, Si 1-x Ge x /Si, are frequently introduced in the device fabrication process. Epitaxy, condensation and annealing processes are commonly used. Since a small variation in composition, strain and crystallinity can result in reduced device performance or failure, the composition, strain and crystallinity must be carefully monitored and controlled throughout the manufacturing process. We have studied the dependence of Ge and Si intermixing on annealing temperature and Raman excitation wavelength. Using multiwavelength Raman spectroscopy, we found Ge and Si intermixing in epitaxially grown Ge(100)/Si(100) after successive thermal anneals. Very strong dependence of signal-to-noise (S/N) ratio measurements on excitation wavelength and film structure was observed. Suitable excitation wavelengths must be chosen to properly characterize Si and Ge-based heteroepitaxial layers based on the thickness, stacking order and composition of epitaxial films having different optical properties at different wavelengths.

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Raman study of strain relaxation in Ge on Si

Cited by 14 publications

References 16 publications

Sputter Epitaxial Growth of Flat Germanium Film with Low Threading-Dislocation Density on Silicon (001)

Sputter Epitaxial Growth of Flat Germanium Film with Low Threading-Dislocation Density on Silicon (001)

Sb-mediated Ge growth on singular and vicinal Si(001) surfaces: A surface optical characterization study

Characterization of Hetero-Epitaxial Ge Films on Si Using Multiwavelength Micro-Raman Spectroscopy

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