High hole mobility tin-doped polycrystalline germanium layers formed on insulating substrates by low-temperature solid-phase crystallization

Takeuchi, Wakana; Taoka, Noriyuki; Kurosawa, Masashi; Sakashita, Mitsuo; Nakatsuka, Osamu; Zaima, Shigeaki

doi:10.1063/1.4926507

Cited by 68 publications

(59 citation statements)

References 23 publications

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“…4,5 In fact, polycrystalline GeSn thin films with Sn concentrations beyond the solubility limit have been realized using this technique. [6][7][8] Polycrystalline GeSn thin films grown on an insulator are anticipated as an alternative to polycrystalline Si films, which are currently utilized as a channel material for thin film transistors (TFTs). Amorphous GeSn recrystallizes at a lower temperature than amorphous Si because of its low eutectic temperature (231.1 C); consequently, low-temperature fabrication of TFT products can be established.…”

Section: Introductionmentioning

confidence: 99%

Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations

Takase

Ishimaru

Uchida

et al. 2016

Journal of Applied Physics

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Thermally induced crystallization processes for amorphous GeSn thin films with Sn concentrations beyond the solubility limit of the bulk crystal Ge-Sn binary system have been examined by X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, and (scanning) transmission electron microscopy. We paid special attention to the behavior of Sn before and after recrystallization. In the as-deposited specimens, Sn atoms were homogeneously distributed in an amorphous matrix. Prior to crystallization, an amorphous-to-amorphous phase transformation associated with the rearrangement of Sn atoms was observed during heat treatment; this transformation is reversible with respect to temperature. Remarkable recrystallization occurred at temperatures above 400 °C, and Sn atoms were ejected from the crystallized GeSn matrix. The segregation of Sn became more pronounced with increasing annealing temperature, and the ejected Sn existed as a liquid phase. It was found that the molten Sn remains as a supercooled liquid below the eutectic temperature of the Ge-Sn binary system during the cooling process, and finally, β-Sn precipitates were formed at ambient temperature.

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Section: Introductionmentioning

confidence: 99%

Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations

Takase

Ishimaru

Uchida

et al. 2016

Journal of Applied Physics

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“…2(d). Since the crystallization temperature of a-Ge is generally above 400 °C, 8,9) this case, the crystallization of the top a-Ge layer at 300 °C, is likely due to the catalytic effect of Ag atoms. 33,34) Therefore, Ag diffusion into the top a-Ge layer is a possible reason why the dendrite growth, i.e., layer exchange, stopped.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4] Researchers have developed the following growth techniques for poly-Ge thin films on insulators: magnetron sputtering, 4) chemical vapor deposition, 5) laser annealing, 6,7) and solid-phase crystallization (SPC). 8,9) Those poly-Ge thin films, however, consist of small grains (< 1 μm) and their carrier mobilities are limited to 140 cm 2 V -1 s -1 . 4,8,9) In addition, because vacancies in Ge act as acceptors, the poly-Ge thin films are highly p-doped (> 5 × 10 17 cm -3 ).…”

Section: Introductionmentioning

confidence: 99%

“…8,9) Those poly-Ge thin films, however, consist of small grains (< 1 μm) and their carrier mobilities are limited to 140 cm 2 V -1 s -1 . 4,8,9) In addition, because vacancies in Ge act as acceptors, the poly-Ge thin films are highly p-doped (> 5 × 10 17 cm -3 ). 8,9) The high carrier concentration makes it difficult to control the conduction type.…”

Section: Introductionmentioning

confidence: 99%

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Effect of interlayer on silver-induced layer exchange crystallization of amorphous germanium thin film on insulator

Yoshimine¹,

Toko²,

Suemasu³

2017

Jpn. J. Appl. Phys.

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Metal-induced layer exchange (MILE) is an advanced crystallization technique for fabricating high-quality semiconductor thin films on insulating substrates at low temperatures. Here, we focused on Ag as a catalytic metal for crystallizing amorphous germanium thin films on glass through MILE. The layer exchange between Ag and aGe was not simple because Ag diffused into aGe so fast that it crystallized the top aGe layer before the completion of layer exchange. To suppress Ag diffusion into aGe , we explored the kind of interlayer material between them as well as the growth temperature. Preparing SiO2 and GeO2 interlayers allowed for a complete layer exchange, resulting in the formation of polycrystalline Ge thin films on glass at temperatures as low as 250 °C. These findings are essential for further understanding and controlling the layer exchange phenomenon.

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“…As mentioned above, therefore, to take advantage of the superior properties of Ge, poly‐Ge thin films have been investigated as a low‐cost substitute for the expensive single crystalline Ge substrates for large‐area electronic and photovoltaic applications. Recently, several crystallization processes for α ‐Ge have been reported to obtain high quality poly‐Ge films such as solid phase crystallization (SPC), laser annealing, and metal‐induced crystallization (MIC) . However, crystallization of α ‐Ge with SPC process requires high annealing temperature around 500°C, which is too high for inexpensive substrates.…”

Section: Introductionmentioning

confidence: 99%

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

Kabaçelik

Kulakçı

Turan

et al. 2018

Surface & Interface Analysis

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Gold-induced (Au-) crystallization of amorphous germanium (α-Ge) thin films was investigated by depositing Ge on aluminum-doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X-ray diffraction, and scanning electron microscopy. The Raman and X-ray diffraction results indicated that the Au-induced crystallization of the Ge films yielded crystallization at temperature as low as 300°Cfor 1 hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500°C for 1 hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current-voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73 Scm −1 for annealed samples grown on aluminum-doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge-based electronic and photovoltaic applications.

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High hole mobility tin-doped polycrystalline germanium layers formed on insulating substrates by low-temperature solid-phase crystallization

Cited by 68 publications

References 23 publications

Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations

Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations

Effect of interlayer on silver-induced layer exchange crystallization of amorphous germanium thin film on insulator

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

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