Almost pinning-free bismuth/Ge and /Si interfaces

Nishimura, Tomonori; Luo, Xuan; Matsumoto, Soshi; Yajima, Takeaki; Toriumi, Akira

doi:10.1063/1.5115535

Cited by 13 publications

(16 citation statements)

References 20 publications

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“…Recently, Shen et al reported the low contact resistance between semimetal bismuth and monolayer MoS 2 . Bismuth is a semimetal that has a very low density of states around E F , which provides weak pinning of its SBHs on Bi or similar Sb when contacting to 2D materials or Si. , However, Bi has a relatively lower melting point of only 271 °C, thus Bi contacts will melt during back-end-of-line (BEOL) processing. Sb with a higher melting point of 631 °C is able to survive BEOL temperature …”

Section: Resultsmentioning

confidence: 99%

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS₂/Metal Schottky Barriers

Zhang

Guo

Robertson

2022

ACS Appl. Mater. Interfaces

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Weaker Fermi level pinning (FLP) at the Schottky barriers of 2D semiconductors is electrically desirable as this would allow a minimizing of contact resistances, which presently limit device performances. Existing contacts on MoS 2 have a strong FLP with a small pinning factor of only ∼0.1. Here, we show that Moire interfaces can stabilize physisorptive sites at the Schottky barriers with a much weaker interaction without significantly lengthening the bonds. This increases the pinning factor up to ∼0.37 and greatly reduces the n-type Schottky barrier height to ∼0.2 eV for certain metals such as In and Ag, which can have physisorptive sites. This then accounts for the low contact resistance of these metals as seen experimentally. Such physisorptive interfaces can be extended to similar systems to better control SBHs in highly scaled 2D devices.

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Section: Resultsmentioning

confidence: 99%

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS₂/Metal Schottky Barriers

Zhang

Guo

Robertson

2022

ACS Appl. Mater. Interfaces

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“…[31] To overcome the difficulty in reproducibility and in the deterministic definition of the metal phase in metal-Si/Ge heterostructures, [32] contacts composed of singleelement metals are a highly rewarding strategy for diverse next-generation nanoelectronic, optoelectronic, and quantum devices [33][34][35][36] as well as for providing strategies for pinning-free contacts as shown recently with Bi/Si and Bi/Ge contact systems. [17] Despite a vast variety of different nanoelectronic, [37,38] optoelectronic, [39,40] and superconductor-semiconductor hybrid devices [41][42][43] based on Si 1−x Ge x layers of various compositions, a systematic investigation of the structural and electronic properties of Al-Si 1−x Ge x heterostructures obtained from a thermally induced Al-Si 1−x Ge x exchange is still not available. In this respect, the work at hand discusses the Si 1−x Ge x compositiondependent properties of SBFETs based on monolithic and single-crystalline heterostructures with abrupt and flat junctions.…”

Section: Introductionmentioning

confidence: 99%

“…Lately, the use of Bismuth contacts having a comparatively low electron density, have successfully shown to minimize pinning effects in Si and Ge. [ 17 ] Nevertheless, as dimensions of semiconductor devices scale down, precise dopant control and thus contact properties get affected by statistical variability in dopant concentration. [ 18 ] Additionally, surface depletion effects and even the dielectric mismatch between the semiconductor region and the surrounding insulator induce severe problems.…”

Section: Introductionmentioning

confidence: 99%

Composition Dependent Electrical Transport in Si_1−xGe_xNanosheets with Monolithic Single‐Elementary Al Contacts

Wind

Sistani

Böckle

et al. 2022

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and drain electrodes in highly scaled p-channel field-effect transistors (FETs) for the realization of very-large-scale integration (VLSI) systems. [1] Despite these efforts, the continuous scaling of metaloxide-semiconductor field-effect transistors (MOSFETs) is approaching physical limits where the nature of deterministic charge carrier separation between source and drain by an energy barrier is not applicable anymore. [2,3] In the quest of overcoming scaling limitations, new lines of research arose. Device research has shifted toward new architectures, materials, and technologies to enable "More than Moore" paradigms, [4] extending the mature Si complementary metal-oxidesemiconductor (CMOS) platform. [5] In this regard, Si 1−x Ge x and Ge active regions integrated on Si platforms are promising candidates for future optoelectronic devices [6] and the realization of energy efficient steep subthreshold switches such as band-to-band tunneling transistors (TFETs), [7,8] negative capacitance Ge nanowire FETs, [9,10] and positive feedback FETs. [11] Conventionally, degenerately doped semiconductor regions in combination with thin layers made of transition-metal semiconductor alloys, such as metalsilicides [12] and metal-germanides, [13] have been used to obtain ohmic contacts to most Si 1−x Ge x and Ge based devices. Toward the achievement of ohmic contacts, pinning-free metal semiconductor contacts have been explored in Si and Ge through Si 1−x Ge x is a key material in modern complementary metal-oxide-semiconductor and bipolar devices. However, despite considerable efforts in metal-silicide and -germanide compound material systems, reliability concerns have so far hindered the implementation of metal-Si 1−x Ge x junctions that are vital for diverse emerging "More than Moore" and quantum computing paradigms. In this respect, the systematic structural and electronic properties of Al-Si 1−x Ge x heterostructures, obtained from a thermally induced exchange between ultrathin Si 1−x Ge x nanosheets and Al layers are reported. Remarkably, no intermetallic phases are found after the exchange process. Instead, abrupt, flat, and void-free junctions of high structural quality can be obtained. Interestingly, ultra-thin interfacial Si layers are formed between the metal and Si 1−x Ge x segments, explaining the morphologic stability. Integrated into omega-gated Schottky barrier transistors with the channel length being defined by the selective transformation of Si 1−x Ge x into single-elementary Al leads, a detailed analysis of the transport is conducted. In this respect, a report on a highly versatile platform with Si 1−x Ge x composition-dependent properties ranging from highly transparent contacts to distinct Schottky barriers is provided. Most notably, the presented abrupt, robust, and reliable metal-Si 1−x Ge x junctions can open up new device implementations for different types of emerging nanoelectronic, optoelectronic, and quantum devices.

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“…This heterojunction is notable because Sb is a semimetal that has a very low density of states (DOS) around EF. Experimentally, Bi contacts on Ge were found to be ohmic [24], and this is partly attributed to the low DOS at EF which provides only weak pinning of metal SBHs on Bi or Sb, as shown in Fig. 10(a).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the MIGS model fails to explain the orientation dependence of SBHs for epitaxial NiSi2/Si interfaces [15,16] or for germanide/Ge interfaces [17], the termination dependence of (Sc, Er)As /GaAs interfaces [18] or the weak pinning at the Bi/Si interfaces [24,25]. These various interfaces all show weaker FLP (larger S) and an orientation dependence of SBHs [15][16][17][18], which cannot be described by the basic MIGS model.…”

Section: Introductionmentioning

confidence: 99%

Extending the metal-induced gap state model of Schottky barriers

Robertson

Guo

Zhang

et al. 2020

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Fermi level pinning at Schottky barriers strongly limits the minimization of contact resistances in devices and thereby limits the scaling of modern Si electronic devices, so it is useful to understand the full range of behaviors of Schottky barriers. We find that some semiconductor interfaces with compound metals like silicides have apparently weaker Fermi level pinning. This occurs as these metals have an underlying covalent skeleton, whose interfaces with semiconductors lead to mis-coordinated defect sites that create additional localized interface states that go beyond the standard metal-induced gap states (MIGS) model of Schottky barriers. This causes a stronger dependence of Schottky barrier height (SBH) on the metal and on interface orientation. These states are argued to be an additional component needed to extend the MIGS model.

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Almost pinning-free bismuth/Ge and /Si interfaces

Cited by 13 publications

References 20 publications

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS₂/Metal Schottky Barriers

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS₂/Metal Schottky Barriers

Composition Dependent Electrical Transport in Si_1−xGe_xNanosheets with Monolithic Single‐Elementary Al Contacts

Extending the metal-induced gap state model of Schottky barriers

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Almost pinning-free bismuth/Ge and /Si interfaces

Cited by 13 publications

References 20 publications

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS2/Metal Schottky Barriers

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS2/Metal Schottky Barriers

Composition Dependent Electrical Transport in Si1−xGexNanosheets with Monolithic Single‐Elementary Al Contacts

Extending the metal-induced gap state model of Schottky barriers

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Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS₂/Metal Schottky Barriers

Reduced Fermi Level Pinning at Physisorptive Sites of Moire-MoS₂/Metal Schottky Barriers

Composition Dependent Electrical Transport in Si_1−xGe_xNanosheets with Monolithic Single‐Elementary Al Contacts