The effect of antimony-doping on Ge2Sb2Te5, a phase change material

Choi, Kyu-Jeong; Yoon, Sung‐Min; Lee, Nam-Yeal; Lee, Seung-Yun; Park, Young-Sam; Yu, Byoung–Gon; Ryu, Sang-Ouk

doi:10.1016/j.tsf.2008.02.014

Cited by 37 publications

(24 citation statements)

References 10 publications

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“…The clear SET operations thanks to the perfect crystallization in moderate time can preferably do good for the retention behaviors even at a relatively hightemperature. We have confirmed that the Sb22-GST showed a longer incubation time for crystallization than the GST at the temperature of 30 C lower than the crystallization temperature of films with given compositions [13]. These results suggest that Sb22-GST show better retention characteristics especially at a higher temperature, although the evaluation for the devices should be carried out for future works.…”

Section: Resultssupporting

confidence: 68%

“…It can be confirmed for the GST225 that the sheet resistance appears to drop with two-steps at 160 C and 320 C with the increase of temperature. The first and second drops reflect the phase-transition from an amorphous to a less conductive metastable fcc phase and from an fcc phase to a more conductive stable hcp phase, respectively [13]. It is possible that these two crystalline phases are simultaneously formed at each SET operation with an irregular mixing ratio within the device operating volume, which causes the R SET fluctuation.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, we have proposed the use of Sb-rich nonstoichiometric composition of Ge-Sb-Te-based (GST) chalcogenide alloy for more reliable memory operations of the PCM owing to its distinct features such as the direct phase-transition from an amorphous to an hcp crystalline phase without the appearance of a metastable fcc phase and the improvement of high-temperature stability of the amorphous phase. Phase-transition behaviors of the Sb-rich GST alloy films were confirmed in the X-ray diffraction analysis and four-point probe method as the changes in crystal structures and in sheet resistances, respectively [13]. Although, some problems such as a decrease of crystallization speed [14] and undesirable interdiffusion between Sb added to excess and electrodes [15] were observed, the compositional stability during repetitive rewritable operations and the decrease of threshold voltage V th for electronic switching were confirmed in actual devices employing Sb-rich GST [14].…”

Section: Introductionmentioning

confidence: 95%

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Improvement of operational stability in SET states of phase-change-type nonvolatile memory devices using Sb-rich phase of Ge–Sb–Te alloys

Yoon

Lee

Jung

et al. 2009

Solid-State Electronics

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Section: Resultssupporting

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

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Improvement of operational stability in SET states of phase-change-type nonvolatile memory devices using Sb-rich phase of Ge–Sb–Te alloys

Yoon

Lee

Jung

et al. 2009

Solid-State Electronics

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“…The resulting reduction of free carriers could then increase the minimum GST thickness required for the improved TFT performance, and thus the crystallization process could be simplified. Furthermore, a significant increase of the Sb content has resulted in reduced resistivities in the amorphous phase of GST [51], which could be a path for improvements of TFTs with amorphous GST channels.…”

Section: Discussionmentioning

confidence: 99%

Ge2Sb2Te5 p-Type Thin-Film Transistors on Flexible Plastic Foil

et al. 2018

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In this work, we show the performance improvement of p-type thin-film transistors (TFTs) with Ge2Sb2Te5 (GST) semiconductor layers on flexible polyimide substrates, achieved by downscaling of the GST thickness. Prior works on GST TFTs have typically shown poor current modulation capabilities with ON/OFF ratios ≤20 and non-saturating output characteristics. By reducing the GST thickness to 5 nm, we achieve ON/OFF ratios up to ≈300 and a channel pinch-off leading to drain current saturation. We compare the GST TFTs in their amorphous (as deposited) state and in their crystalline (annealed at 200 °C) state. The highest effective field-effect mobility of 6.7 cm2/Vs is achieved for 10-nm-thick crystalline GST TFTs, which have an ON/OFF ratio of ≈16. The highest effective field-effect mobility in amorphous GST TFTs is 0.04 cm2/Vs, which is obtained in devices with a GST thickness of 5 nm. The devices remain fully operational upon bending to a radius of 6 mm. Furthermore, we find that the TFTs with amorphous channels are more sensitive to bias stress than the ones with crystallized channels. These results show that GST semiconductors are compatible with flexible electronics technology, where high-performance p-type TFTs are strongly needed for the realization of hybrid complementary metal-oxide-semiconductor (CMOS) technology in conjunction with popular n-type oxide semiconductor materials.

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“…3 Critical challenges for fabrication of PCM devices are the continued downscaling and reduction of the reset/set currents. 3,4 One way to solve these problems is the transition to a three-dimensional structure, where the chalcogenide material is filled into a contact hole. 5 However, conventional physical vapor deposition techniques are not suitable for the required filling process due to poor step coverage.…”

mentioning

confidence: 99%

Hot Wire Chemical Vapor Deposition of Ge[sub 2]Sb[sub 2]Te[sub 5] Thin Films

Reso

Šilinskas

Kalkofen

et al. 2011

J. Electrochem. Soc.

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Germanium-antimony-telluride or, particularly, Ge 2 Sb 2 Te 5 ͑GST͒ thin films were deposited by hot wire ͑HW͒ chemical vapor deposition ͑CVD͒. Tetraallylgermanium, triisopropylantimony, and diisopropyltelluride were used as precursors for germanium, antimony, and tellurium, respectively. The influence of deposition parameters, such as temperature, pressure, and hydrogen content, was investigated. It was found that higher temperature, higher pressure, and lower hydrogen flow yielded higher growth rates of the films. An admixture of hydrogen reduced the Te concentration in the GST thin films and enhanced the content of Ge and Sb. The chemical composition could also be altered by other deposition parameters but these dependencies were not as well pronounced as in the hydrogen case. Generally, a higher Ge concentration was related to a smaller amount of Te. The films deposited at a higher pressure showed a significantly higher roughness. In addition, the switching from a low to high resistivity state was tested.Phase-change memories ͑PCM͒ are one of the most promising candidates for the next generation of nonvolatile memories. 1 GeSb-Te alloys or, particularly, the Ge 2 Sb 2 Te 5 compound are very attractive and commonly used materials for PCM applications, 2,3 where the reversible transition between crystalline and amorphous phases is utilized. 2-4 The crystalline and amorphous phases correspond to the low resistivity state and the high resistivity state, respectively. The switching between these two states is obtained by Joule heating or, in particular, by a short and large current pulse for the conversion of GST from a low to high resistivity ͑reset operation͒ and by a longer and relatively small current pulse for the transition from a high resistivity to a low one ͑set operation͒. 3 Critical challenges for fabrication of PCM devices are the continued downscaling and reduction of the reset/set currents. 3,4 One way to solve these problems is the transition to a three-dimensional structure, where the chalcogenide material is filled into a contact hole. 5 However, conventional physical vapor deposition techniques are not suitable for the required filling process due to poor step coverage. Therefore, it is necessary to use deposition methods such as chemical vapor deposition ͑CVD͒ or atomic layer deposition ͑ALD͒ that offer a better conformity and composition control. 5,6 Recently, CVD and ALD have been used for producing the ternary Ge-Sb-Te films. 5-9 However, film quality problems, such as film uniformity, roughness, etc., are always an issue for the films deposited by conventional CVD. 7,9 On the other hand, Abrutis et al. 6 and Choi et al. 10 showed that a precursor activation within the CVD process yields a lower surface roughness and a better lateral growth. In addition, activation by a hot wire ͑HW͒ enables the use of a wider range of precursors because of its catalytic character of precursor decomposition. 6 This was also observed in our previous work, 11,12 where detailed comparison between conventional an...

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The effect of antimony-doping on Ge2Sb2Te5, a phase change material

Cited by 37 publications

References 10 publications

Improvement of operational stability in SET states of phase-change-type nonvolatile memory devices using Sb-rich phase of Ge–Sb–Te alloys

Improvement of operational stability in SET states of phase-change-type nonvolatile memory devices using Sb-rich phase of Ge–Sb–Te alloys

Ge2Sb2Te5 p-Type Thin-Film Transistors on Flexible Plastic Foil

Hot Wire Chemical Vapor Deposition of Ge[sub 2]Sb[sub 2]Te[sub 5] Thin Films

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