Increase in current density for metal contacts to n-germanium by inserting TiO2 interfacial layer to reduce Schottky barrier height

Lin, Jiunn-Yuan; Roy, Arunanshu M.; Nainani, Aneesh; Sun, Yun; Saraswat, Krishna C.

doi:10.1063/1.3562305

Cited by 117 publications

(81 citation statements)

References 12 publications

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“…It has been demonstrated that thin tunneling barriers with low conduction band-offset (CBO or DEc) to Ge could achieve higher currents and thus enable low resistance metal-insulator-semiconductor (MIS) contacts to Ge. 16 The insertion of such thin tunnel barriers including Al 2 O 3 , 14 SiN 3 , 15 TiO 2 , 16 and ZnO (Ref. 17) to form MIS contacts has been shown to reduce the Schottky barrier height as well as facilitate the unpinning of Fermi-level in n-type Ge.…”

Section: Introductionmentioning

confidence: 99%

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

Jain

Zhu

Maurya

et al. 2014

Journal of Applied Physics

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We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO 2 ) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO 2 thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO 2 thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO 2 /Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 6 0.02 eV was determined for the amorphous TiO 2 thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO 2 /Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO 2 /Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of DE V (100) > DE V (111) > DE V (110) and a conduction band-offset relation of DE C (110) > DE C (111) > DE C (100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO 2 for potential high-j dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors. V C 2014 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 99%

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

Jain

Zhu

Maurya

et al. 2014

Journal of Applied Physics

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“…In Ge, like in other semiconductor systems, a robust and low-ohmic metal contacting 1 is needed for the successful fabrication of (opto-)electronic devices. However, critical technological hazards posed by the diffusion of the contacting metal into the Ge to form large aluminide or germanide clusters 2 and also the high Schottky barrier height of n-type Ge to metals 3 continue to present problems in need of solutions. In Ge photodiode fabrication, nickel (Ni) can, for example, be used as a barrier/contacting metal together with gold (Au) to achieve low contact resistance.…”

Section: Introductionmentioning

confidence: 99%

Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

Sammak

Nanver

2015

Journal of Elec Materi

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The effectiveness of using nanometer-thin boron (PureB) layers as interdiffusion barrier to aluminum (Al) is studied for a contacting scheme specifically developed for fabricating germanium-on-silicon (Ge-on-Si) p + n photodiodes with an oxide-covered light entrance window. Contacting is achieved at the perimeter of the Ge-island anode directly to an Al interconnect metallization. The Ge is grown in oxide windows to the Si wafer and covered by a B and gallium (Ga) layer stack (PureGaB) composed of about a nanometer of Ga for forming the p + Ge region and 10 nm of B as an interdiffusion barrier to the Al. To form contact windows, the side-wall oxide is etched away, exposing a small tip of the Ge perimeter to Al that from this point travels about 5 lm into the bulk Ge crystal. In this process, Ge and Si materials are displaced, forming Ge-filled V-grooves at the Si surface. The Al coalesces in grains. This process is studied here by high-resolution cross-sectional transmission electron microscopy and energy dispersive x-ray spectroscopy that confirm the purities of the Ge and Al grains. Diodes are fabricated with different geometries and statistical current-voltage characterization reveals a spread that can be related to across-the-wafer variations in the contact processing. The I-V behavior is characterized by low dark current, low contact resistance, and breakdown voltages that are suitable for operation in avalanching modes. The restricted access to the Ge of the Al inducing the Ge and Si material transport does not destroy the very good electrical characteristics typical of PureGaB Ge-on-Si diodes.

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“…The advantage of the MIS contacts is most pronounced at relatively low doping levels, but it diminishes gradually with increasing N d -at ultrahigh doping levels, even the "ideal" MIS, A, cannot outperform its MS counterpart, D. Moreover, the existence of such an "ideal" MIS as A is suspicious: for instance, insulators with m Ã ti as low as 0.2 m 0 are uncommon; 46,50 insulators that have low DE C with semiconductors are rare; 44,46,50 moreover, there is usually a minimal insulator thickness of >1 nm required for an MIS to lower / b to 0.1 eV. 5,7,9,13 In conclusion, the MIS contacts are more appealing to the applications that use relatively low doped semiconductors, such as compound semiconductor devices and Si solar cells, while the MS contacts will still be the major force to push q c down below 1 Â 10 À8 XÁcm 2 to meet the Complementary Metal-Oxide-Semiconductor (CMOS) requirement for the 10 nm technology node and beyond. 51 In summary, this paper systematically compares the contact resistivity of the MIS and MS contacts.…”

Section: Contact Resistivities Of Metal-insulator-semiconductor Contamentioning

confidence: 99%

Contact resistivities of metal-insulator-semiconductor contacts and metal-semiconductor contacts

Schaekers

Barla

Horiguchi

et al. 2016

Applied Physics Letters

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Applying simulations and experiments, this paper systematically compares contact resistivities (ρc) of metal-insulator-semiconductor (MIS) contacts and metal-semiconductor (MS) contacts with various semiconductor doping concentrations (Nd). Compared with the MS contacts, the MIS contacts with the low Schottky barrier height are more beneficial for ρc on semiconductors with low Nd, but this benefit diminishes gradually when Nd increases. With high Nd, we find that even an “ideal” MIS contact with optimized parameters cannot outperform the MS contact. As a result, the MIS contacts mainly apply to devices that use relatively low doped semiconductors, while we need to focus on the MS contacts to meet the sub-1 × 10−8 Ω cm2 ρc requirement for future Complementary Metal-Oxide-Semiconductor (CMOS) technology.

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Increase in current density for metal contacts to n-germanium by inserting TiO2 interfacial layer to reduce Schottky barrier height

Cited by 117 publications

References 12 publications

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

Contact resistivities of metal-insulator-semiconductor contacts and metal-semiconductor contacts

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