Barrier heights of Schottky contacts on strained AlGaN/GaN heterostructures: Determination and effect of metal work functions

AbstractSchottky source/drain (S/D) in Si-CMOS provide an alternative to current approaches in S/D, channel, and gate-stack engineering. The Schottky S/D PMOS has been demonstrated at a number of university and industrial laboratories. The bottleneck for the Schottky S/D NMOS is the fact that none of the common metals or metal silicides has a low enough barrier height (~0.2 eV) on n-type Si. A method to produce low Schottky barriers on n-type Si with common metals including aluminum (Al) and chromium (Cr) is reported in this paper. The interface between metal and Si(100) is engineered at the atomic scale with a monolayer of selenium (Se) to reduce the density of interface states, and the engineered interface shows inertness to chemical and electronic processes at the interface. One consequence of this electronic inertness is that the Schottky barrier is now more dependent on the metal work function. Al and Cr both have work functions very close to the Si electron affinity. It is found that the Schottky barrier of Al on Se-engineered n-type Si(100) is 0.08 eV, and that of Cr is 0.26 eV. These numbers agree well with the ideal Schottky barrier heights for Al and Cr on n-type Si(100), but are significantly different from the barrier heights known for four decades for these metals on n-type Si(100). These results bring new hope for the Schottky S/D NMOS with a metal commonly used in the Si industry.

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A method for measuring barrier heights, metal work functions and fixed charge densities in metal/SiO2/Si capacitors

Applied Physics Letters ◽

10.1063/1.1489098 ◽

2002 ◽

Vol 80 (25) ◽

pp. 4858-4860 ◽

Cited By ~ 38

Author(s):

Sufi Zafar ◽

Cyril Cabral ◽

R. Amos ◽

A. Callegari

Keyword(s):

Fixed Charge ◽

Charge Densities ◽

Barrier Heights ◽

Work Functions ◽

Metal Work

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Erratum: “A method for measuring barrier heights, metal work functions and fixed charge densities in metal/SiO2/Si capacitors”[Appl. Phys. Lett. 80, 4858 (2002)]

Applied Physics Letters ◽

10.1063/1.2006219 ◽

2005 ◽

Vol 87 (5) ◽

pp. 059901

Author(s):

Sufi Zafar ◽

Cyril Cabral ◽

R. Amos ◽

A. Callegari

Keyword(s):

Fixed Charge ◽

Charge Densities ◽

Barrier Heights ◽

Work Functions ◽

Metal Work

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Microstructure studies of tungsten silicide schottky contacts on Gaas

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126445 ◽

1987 ◽

Vol 45 ◽

pp. 328-329

Author(s):

Yih-Cheng Shih ◽

E. L. Wilkie

Keyword(s):

Thermal Stability ◽

Field Effect Transistors ◽

Schottky Contact ◽

Schottky Contacts ◽

Excellent Thermal Stability ◽

Barrier Heights ◽

Gaas Substrates ◽

Film Adhesion ◽

Threshold Voltages ◽

Thermal Stability Of

Tungsten silicides (WSix) have been successfully used as the gate materials in self-aligned GaAs metal-semiconductor-field- effect transistors (MESFET). Thermal stability of the WSix/GaAs Schottky contact is of major concern since the n+ implanted source/drain regions must be annealed at high temperatures (∼ 800°C). WSi0.6 was considered the best composition to achieve good device performance due to its low stress and excellent thermal stability of the WSix/GaAs interface. The film adhesion and the uniformity in barrier heights and ideality factors of the WSi0.6 films have been improved by depositing a thin layer of pure W as the first layer on GaAs prior to WSi0.6 deposition. Recently WSi0.1 has been used successfully as the gate material in 1x10 μm GaAs FET's on the GaAs substrates which were sputter-cleaned prior to deposition. These GaAs FET's exhibited uniform threshold voltages across a 51 mm wafer with good film adhesion after annealing at 800°C for 10 min.

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Metal Contacts on a-GaN

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300002131 ◽

1996 ◽

Vol 1 ◽

Cited By ~ 7

Author(s):

T. U. Kampen ◽

W. Mönch

Keyword(s):

Tight Binding ◽

Image Force ◽

Schottky Contacts ◽

Metal Contacts ◽

Zero Bias ◽

Barrier Heights ◽

Current Voltage ◽

Optical Dielectric Constant ◽

Optical Dielectric ◽

Gap States

The Schottky barrier heights of silver and lead contacts on n-type GaN (0001) epilayers were determined from current-voltage characteristics. The zero-bias barrier heights and the ideality factors were found to be linearly correlated. Similar observations were previously reported for metal contacts on Si (111) and GaAs (110) surfaces. The barrier heights of ideal Schottky contacts are characterized by image force lowering of the barrier only. This gives an ideality factor of 1.01. From our data we obtain barrier heights of 0.82 eV and 0.73eV for ideal Ag and Pb contacts on GaN, respectively. The metal-induced gap states (MIGS) model predicts the barrier heights of ideal Schottky contacts on a given semiconductor to be linearly correlated with the electronegativities of the metals. The two important parameters of this MIGS-and-electronegativity model are the charge neutrality level (CNL) of the MIGS and a slope parameter. The CNL may be calculated from the dielectric band gap and using the empirical tight-binding method. The slope parameters are given by the optical dielectric constant of the respective semiconductor. The predictions of the MIGS model for metal/GaN contacts are confirmed by the results presented here and by barrier heights previously reported by others for Au, Ti, Pt, and Pd contacts on GaN.

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Passivation of Gaas by Novel P2S5/(NH4)2Sx Sulfurization Techniques

MRS Proceedings ◽

10.1557/proc-281-659 ◽

1992 ◽

Vol 281 ◽

Author(s):

J. T. Hsieh ◽

C. Y. Sun ◽

H. L. Hwang

Keyword(s):

Photoelectron Spectroscopy ◽

Surface Passivation ◽

Schottky Diodes ◽

Lower Surface ◽

State Density ◽

Surface Band ◽

Band Bending ◽

Barrier Heights ◽

Effective Barrier ◽

Metal Work

ABSTRACTA new surface passivation technique using P2S5/(NH4)2S on GaAs was investigated, and the results are compared with those of the (NH4)2Sx treatment. With this new surface treatment, the effective barrier heights for both Al- and Au—GaAs Schottky diodes were found to vary with the metal work functions, which is a clear evidence of the lower surface state density. Results of I—V measurements show that P2S5/(NH4)2S—passivated diodes have lower reverse leakage current and higher effective barrier height than those of the (NH4)2Sx -treated ones. Auger Electron Spectroscopy, X—ray photoelectron spectroscopy and Raman scattering measurements were done to characterize the surfaces including their compositions and surface band bending. In this paper, interpretations on this novel passivation effect is also provided.

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Phase Inhomogeneity and Electrical Characteristics of Nickel Silicide Schottky Contacts Formed on 4H-SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.615-617.577 ◽

2009 ◽

Vol 615-617 ◽

pp. 577-580 ◽

Cited By ~ 4

Author(s):

Irina P. Nikitina ◽

Konstantin Vassilevski ◽

Alton B. Horsfall ◽

Nicolas G. Wright ◽

Anthony G. O'Neill ◽

...

Keyword(s):

Nickel Silicide ◽

Schottky Contacts ◽

Electrical Characteristics ◽

Adhesion Layer ◽

Temperature Range ◽

Barrier Heights ◽

Phase Inhomogeneity ◽

Layer 4 ◽

State Chemical ◽

Nisi Phase

Nickel silicide Schottky contacts were formed on 4H-SiC by consecutive deposition of a titanium adhesion layer, 4 nm thick, and nickel, 100 nm thick, followed by annealing at temperatures from 600 to 750 °C. It was found that contacts with barrier heights of 1.45 eV, consisting mainly of NiSi phase, formed in the 600-660 °C temperature range, while annealing at around 750 °C led to the formation of Ni2Si phase with barrier heights of 1.1 eV. Annealing at intermediate temperatures resulted in the nucleation of Ni2Si grains embedded in the NiSi film which were directly observed by micro-Raman mapping. It was concluded that the thermodynamically unfavourable NiSi phase appeared in the 600-660 °C temperature range due to the fact that the solid state chemical reaction between Ni and SiC at these temperatures is controlled by nickel diffusion through the titanium barrier.

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Trap-assisted tunnelling current in MIM structures

Open Physics ◽

10.2478/s11534-010-0027-7 ◽

2011 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Juraj Racko ◽

Miroslav Mikolášek ◽

Ralf Granzner ◽

Juraj Breza ◽

Daniel Donoval ◽

...

Keyword(s):

Energy Distribution ◽

Quantum Mechanical ◽

Current Transport ◽

Metal Insulator ◽

Insulating Layer ◽

New Model ◽

Metal Insulator Metal ◽

Work Functions ◽

Metal Work ◽

Tunnelling Current

AbstractA new model is presented of current transport in Metal Insulator Metal (MIM) structures by quantum mechanical tunnelling. In addition to direct tunnelling through an insulating layer, tunnelling via defects present in the insulating layer plays an important role. Examples of the influence of the material and thickness of the insulating layer, energy distribution of traps, and metal work functions are also provided.

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