A crystalline germanium flexible thin-film transistor

Higashi, Hidenori; Nakano, Maasa; Kobayashi, Kazuki; Fujita, Y.; Yamada, Shinya; Kanashima, Takeshi; Tsunoda, Isao; Nakashima, Hiroshi; Hamaya, Kohei

doi:10.1063/1.5007828

Cited by 24 publications

(20 citation statements)

References 29 publications

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“…To date, the low-temperature syntheses of Ge layers have been achieved by using several methods, including solid-phase crystallization (SPC), − laser annealing, − chemical vapor deposition, , seed layer technique, lamp annealing, , and metal-induced crystallization (MIC). − By use of these methods, the operation of flexible TFTs with polycrystalline (poly-) Ge has been reported, , exhibiting higher field-effect mobilities than most flexible TFTs with amorphous, oxide, and organic semiconductors. These results demonstrate the excellent potential of the Ge-based flexible TFTs.…”

Section: Introductionmentioning

confidence: 99%

Record-High Hole Mobility Germanium on Flexible Plastic with Controlled Interfacial Reaction

Imajo

Ishiyama

Saitoh³

et al. 2021

ACS Appl. Electron. Mater.

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A semiconductor thin film with high carrier mobility was fabricated on a flexible film. During the solid-phase crystallization process of the densified amorphous Ge layer, the interfacial reaction with the GeO x underlayer is controlled by the GeO x thickness (0–300 nm) and the growth temperature (375–450 °C). The appropriate amount of oxygen diffusion from GeO x to Ge produces large Ge grains (up to 13 μm in diameter) with high crystal quality. The use of a high heat-resistant polyimide film allows postannealing at 500 °C and improves the hole mobility of Ge to 690 cm2 V–1 s–1 while maintaining flexibility. This hole mobility is higher than that of any other semiconductor thin films directly formed on insulators, including single-crystal Ge grown at high temperatures, and even higher than that of a Si wafer. The findings open up the possibility of incorporating high-speed transistors on flexible devices that surpass Si metal–oxide–semiconductor field-effect transistors.

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Section: Introductionmentioning

confidence: 99%

Record-High Hole Mobility Germanium on Flexible Plastic with Controlled Interfacial Reaction

Imajo

Ishiyama

Saitoh³

et al. 2021

ACS Appl. Electron. Mater.

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“…Many crystallization techniques have been developed, including solid-phase crystallization (SPC) 14 – 16 , laser annealing 17 , 18 , chemical vapor deposition 19 , 20 , flash-lamp annealing 21 , the seed layer technique 22 , and metal-induced crystallization 23 – 25 . By using these techniques, Ge-TFTs have been fabricated on thermally oxidized Si 21 , 26 , 27 , glass 28 – 31 , and even flexible substrates 22 , 32 . Since gate stack technology for Ge has developed sufficiently 8 , recent Ge-TFTs performance is limited by the properties of the poly-Ge thin film itself 21 , 22 , 26 – 32 .…”

Section: Introductionmentioning

confidence: 99%

“…By using these techniques, Ge-TFTs have been fabricated on thermally oxidized Si 21 , 26 , 27 , glass 28 – 31 , and even flexible substrates 22 , 32 . Since gate stack technology for Ge has developed sufficiently 8 , recent Ge-TFTs performance is limited by the properties of the poly-Ge thin film itself 21 , 22 , 26 – 32 . Some of these TFTs exhibited effective hole mobilities greater than 100 cm 2 /V s 22 , 26 , 28 .…”

Section: Introductionmentioning

confidence: 99%

Improving carrier mobility of polycrystalline Ge by Sn doping

Moto

Yoshimine

Suemasu

et al. 2018

Sci Rep

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To improve the performance of electronic devices, extensive research efforts have recently focused on the effect of incorporating Sn into Ge. In the present work, we investigate how Sn composition x (0 ≤ x ≤ 0.12) and deposition temperature Td (50 ≤ Td ≤ 200 °C) of the Ge1−xSnx precursor affect subsequent solid-phase crystallization. Upon incorporating 3.2% Sn, which is slightly above the solubility limit of Sn in Ge, the crystal grain size increases and the grain-boundary barrier decreases, which increases the hole mobility from 80 to 250 cm2/V s. Furthermore, at Td = 125 °C, the hole mobility reaches 380 cm2/V s, which is tentatively attributed to the formation of a dense amorphous GeSn precursor. This is the highest hole mobility for semiconductor thin films on insulators formed below 500 °C. These results thus demonstrate the usefulness of Sn doping of polycrystalline Ge and the importance of temperature while incorporating Sn. These findings make it possible to fabricate advanced Ge-based devices including high-speed thin-film transistors.

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“…After 10 days of annealing at 300°C, Al regions were interconnected with each other; in other words, layer exchange occurred. Furthermore, there are many studies where the annealing time is too long for Au‐induced layer exchange crystallization . In this study, Au‐rich regions were not interconnected with each other so no layer exchange was observed.…”

Section: Resultsmentioning

confidence: 81%

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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A crystalline germanium flexible thin-film transistor

Cited by 24 publications

References 29 publications

Record-High Hole Mobility Germanium on Flexible Plastic with Controlled Interfacial Reaction

Record-High Hole Mobility Germanium on Flexible Plastic with Controlled Interfacial Reaction

Improving carrier mobility of polycrystalline Ge by Sn doping

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

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