Bilayer metal oxide gate insulators for scaled Ge-channel metal-oxide-semiconductor devices

Swaminathan, Shankar; Shandalov, Michael; Oshima, Yasuhiro; McIntyre, Paul C.

doi:10.1063/1.3313946

Cited by 71 publications

(48 citation statements)

References 15 publications

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“…This will enable future studies to assess ALD of Al 2 O 3 , as well as other feasible high-ĸ candidates and passivation strategies (such as hafnia, zirconia, tantalum, germanium oxynitride [96][97][98][99][100] and bi/tri-layer dielectrics [101][102][103][104] ) on pristine and oxidised Ge surfaces. As such, ReaxFF can be instrumental in identifying optimal processing conditions to form high quality high-ĸ dielectrics/non-Si semiconductor interfaces.…”

Section: Applications Of Reaxffmentioning

confidence: 99%

The ReaxFF reactive force-field: development, applications and future directions

et al. 2016

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The reactive force-field (ReaxFF) interatomic potential is a powerful computational tool for exploring, developing and optimizing material properties. Methods based on the principles of quantum mechanics (QM), while offering valuable theoretical guidance at the electronic level, are often too computationally intense for simulations that consider the full dynamic evolution of a system. Alternatively, empirical interatomic potentials that are based on classical principles require significantly fewer computational resources, which enables simulations to better describe dynamic processes over longer timeframes and on larger scales. Such methods, however, typically require a predefined connectivity between atoms, precluding simulations that involve reactive events. The ReaxFF method was developed to help bridge this gap. Approaching the gap from the classical side, ReaxFF casts the empirical interatomic potential within a bond-order formalism, thus implicitly describing chemical bonding without expensive QM calculations. This article provides an overview of the development, application, and future directions of the ReaxFF method. INTRODUCTIONAtomistic-scale computational techniques provide a powerful means for exploring, developing and optimizing promising properties of novel materials. Simulation methods based on quantum mechanics (QM) have grown in popularity over recent decades due to the development of user-friendly software packages making QM level calculations widely accessible. Such availability has proved particularly relevant to material design, where QM frequently serves as a theoretical guide and screening tool. Unfortunately, the computational cost inherent to QM level calculations severely limits simulation scales. This limitation often excludes QM methods from considering the dynamic evolution of a system, thus hampering our theoretical understanding of key factors affecting the overall behaviour of a material. To alleviate this issue, QM structure and energy data are used to train empirical force fields that require significantly fewer computational resources, thereby enabling simulations to better describe dynamic processes. Such empirical methods, including reactive force-field (ReaxFF), 1 trade accuracy for lower computational expense, making it possible to reach simulation scales that are orders of magnitude beyond what is tractable for QM.Atomistic force-field methods utilise empirically determined interatomic potentials to calculate system energy as a function of atomic positions. Classical approximations are well suited for nonreactive interactions, such as angle-strain represented by harmonic potentials, dispersion represented by van der Waals potentials and Coulombic interactions represented by various polarisation schemes. However, such descriptions are inadequate for modelling changes in atom connectivity (i.e., for modelling chemical reactions as bonds break and form). This motivates the

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Section: Applications Of Reaxffmentioning

confidence: 99%

The ReaxFF reactive force-field: development, applications and future directions

et al. 2016

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“…Recently, the application base for TiO 2 has been growing rapidly, in particular due to its promising properties at nanoscale. Although there have been few reports on the investigation of TiO 2 as a potential high-j gate dielectric on Ge, [24][25][26][27] however, most of the work for TiO 2 integration with Ge has been limited to (100)Ge. To the best of our knowledge, there is only one experimental report on the TiO 2 /Ge band-offset; however, there is no indication of the orientation of 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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“…[3,4] Various groups have reported gate oxides on Ge in MOSFETs, including TiO 2 / Al 2 O 3 , ZrO 2 , LaAlO 3 on an interfacial layer of SrGe x , HfO 2 on an interfacial layer of Y 2 O 3 -doped GeO 2 , Y 2 O 3 on a GeO x interfacial layer, and HfO 2 with Al 2 O 3 to suppress HfO 2 -GeO x intermixing. [5][6][7][8][9][10] Amorphous oxides generally have lower dielectric constants than the crystalline form. However, the absence of grain boundaries in amorphous films is a potential advantage as grain boundaries can serve as defect trap sites.…”

Section: Introductionmentioning

confidence: 99%

Monolithic integration of perovskites on Ge(001) by atomic layer deposition: a case study with SrHfxTi1-xO3

McDaniel

Posadas

et al. 2016

MRS Communications

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This work reports the growth of crystalline SrHf x Ti 1−x O 3 (SHTO) films on Ge (001) substrates by atomic layer deposition. Samples were prepared with different Hf content x to explore if strain, from tensile (x = 0) to compressive (x = 1), affected film crystallization temperature and how composition affected properties. Amorphous films grew at 225°C and crystallized into epitaxial layers at annealing temperatures that varied monotonically with composition from ∼530°C (x = 0) to ∼660°C (x = 1). Transmission electron microscopy revealed abrupt interfaces. Electrical measurements revealed 0.1 A/cm 2 leakage current at 1 MV/cm for x = 0.55.

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Bilayer metal oxide gate insulators for scaled Ge-channel metal-oxide-semiconductor devices

Cited by 71 publications

References 15 publications

The ReaxFF reactive force-field: development, applications and future directions

The ReaxFF reactive force-field: development, applications and future directions

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

Monolithic integration of perovskites on Ge(001) by atomic layer deposition: a case study with SrHfxTi1-xO3

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