A Two-Step Process for the Formation of Au-Ge Ohmic Contacts to n-GaAs

1990 ◽  
Vol 181 ◽  
Author(s):  
M. A. Dornath-Mohr ◽  
M. W. Cole ◽  
H. S. Lee ◽  
C. S. Wrenn ◽  
D. W. Eckart ◽  
...  
Keyword(s):  
Low Temperature ◽  
Barrier Height ◽  
Gaas Substrate ◽  
Ohmic Contacts ◽  
Atomic Percent ◽  
Second Step ◽  
Semiconductor Interface ◽  
Step Process ◽  
Ohmic Behavior

ABSTRACTThe formation of low temperature Au-Ge contacts to n-GaAs is a two-step process. In the first step, the metals segregate into Au and Ge rich regions and the intermixing of the Au and Ge with the Ga and As causes a reduction in the barrier height. The second step occurs after extended annealing, during which time Au and Ge continue to diffuse into the substrate. An orthorhombic Au-Ga phase is formed and it is likely that other Au-Ga or Ge-As phases are formed. The length of the extended anneal is dependent upon the atomic percent of Ge in the film, with the 10 at. % Ge taking 6 hr., the 27 at. % Ge taking 3 hr. and the 50 at. % Ge taking 9 hr. to become ohmic. The 75 at. % Ge sample doesn’t show ohmic behavior even after 33 hr. of annealing. The metal-semiconductor interface configuration appears abrupt, showing no protrusions into the GaAs substrate.

Current Transport Mechanisms in Au-Free Metallizations for CMOS Compatible GaN HEMT Technology

2020 ◽  
Vol 1004 ◽  
pp. 725-730
Author(s):  
Fabrizio Roccaforte ◽  
Monia Spera ◽  
Salvatore Di Franco ◽  
Raffaella Lo Nigro ◽  
Patrick Fiorenza ◽  
...  
Keyword(s):  
Barrier Height ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Large Area ◽  
Si Substrates ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Thermionic Field Emission

Gallium nitride (GaN) and its AlGaN/GaN heterostructures grown on large area Si substrates are promising systems to fabricate power devices inside the existing Si CMOS lines. For this purpose, however, Au-free metallizations are required to avoid cross contaminations. In this paper, the mechanisms of current transport in Au-free metallization on AlGaN/GaN heterostructures are studied, with a focus on non-recessed Ti/Al/Ti Ohmic contacts. In particular, an Ohmic behavior of Ti/Al/Ti stacks was observed after an annealing at moderate temperature (600°C). The values of the specific contact resistance ρc decreased from 1.6×104 Ω.cm2 to 7×105 Ω.cm2 with increasing the annealing time from 60 to 180s. The temperature dependence of ρc indicated that the current flow is ruled by a thermionic field emission (TFE) mechanism, with barrier height values of 0.58 eV and 0.52 eV, respectively. Finally, preliminary results on the forward and reverse bias characterization of Au-free tungsten carbide (WC) Schottky contacts are presented. This contact exhibited a barrier height value of 0.82 eV.

Metal - Gan Contact Technology

1998 ◽  
Vol 514 ◽  
Author(s):  
S. S. Lau
Keyword(s):  
Barrier Height ◽  
Carrier Transport ◽  
Ohmic Contacts ◽  
Accurate Determination ◽  
Surface Cleaning ◽  
Metal Contacts ◽  
Metal Thin Films ◽  
Ohmic Behavior ◽  
Metal Silicides

ABSTRACTIn this talk, we summarize the experimental results obtained on metal-GaN interactions in our laboratory. These interactions include the epitaxial growth of metal thin films on chemically cleaned GaN surfaces, metal silicides for Schottky contacts and metallization schemes for ohmic contacts. We found that many fcc and hcp metals can grow epitaxially on (0001) GaN surfaces at room temperature without in-situ surface cleaning. Metal silicide contacts (such as PtSi) may be more suitable for high temperature applications than elemental contacts, due to the thermal stability of silicides. The intrinsic mechanisms for ohmic behavior for various metal contacts are not well understood at present. More consistent barrier height values measured experimentally can shed light on this issue. Due to the defective nature of the GaN layers, carrier transport across the metal/GaN interface can be due to a number of transport mechanisms, thus making accurate determination of the barrier height difficult. In spite of these difficulties, it seems possible to draw certain general conclusions on the electrical behavior of metal contacts on n-GaN.

The Materials Properties of a Nickel Based Composite Contact to n-Sic for Pulsed Power Switching

2000 ◽  
Vol 622 ◽  
Author(s):  
M. W. Cole ◽  
P. C. Joshi ◽  
F. Ren ◽  
C. W. Hubbard ◽  
M. C. Wood ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Pulsed Power ◽  
Power Switching ◽  
Semiconductor Interface ◽  
Carbide Phases ◽  
Annealing Temperatures ◽  
Ohmic Behavior ◽  
Reaction Region ◽  
Composite Contact ◽  
Surface Morphologies

ABSTRACTNovel Ni/WSi/Ti/Pt composite Ohmic contacts to n-SiC were investigated as a function of annealing temperatures up to 1000°C. The onset of Ohmic behavior occurred at annealing temperatures of 900°C. Annealing at temperatures between 950°and 1000°C yielded excellent Ohmic behavior. At these temperatures the contact-SiC interface was smooth, defect free and characterized by a narrow Ni2Si reaction region. The annealed contacts possessed atomically smooth surface morphologies and exhibited minimal contact expansion. The residual carbon, resultant from SiC decomposition, was constrained by reaction with the WSi and Ti metallization layers forming carbide phases of W and Ti. The locations of the carbide phases were spatially distant from the metal semiconductor interface. Our results demonstrate that the Ni/WSi/Ti/Pt composite Ohmic contact maintains the desirable electrical properties associated with Ni contacts and possess excellent interfacial, compositional and surface properties which are required for reliable high power and high temperature device operation.

scholarly journals Low Temperature Ni-Al Ohmic Contacts to p-Type 4H-SiC Using Semi-Salicide Processing

2018 ◽  
Vol 924 ◽  
pp. 389-392 ◽  
Author(s):  
Mattias Ekström ◽  
Shuoben Hou ◽  
Hossein Elahipanah ◽  
Arash Salemi ◽  
Mikael Östling ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ohmic Contact ◽  
Thermal Processing ◽  
Ohmic Contacts ◽  
Rapid Thermal Processing ◽  
Nickel Silicide ◽  
Second Step ◽  
Low Resistance ◽  
Annealing Step ◽  
P Type

Most semiconductor devices require low-resistance ohmic contact to p-type doped regions. In this work, we present a semi-salicide process that forms low-resistance contacts (~10-4 Ω cm2) to epitaxially grown p-type (>5×1018 cm-3) 4H-SiC at temperatures as low as 600 °C using rapid thermal processing (RTP). The first step is to self-align the nickel silicide (Ni2Si) at 600 °C. The second step is to deposit aluminium on top of the silicide, pattern it and then perform a second annealing step in the range 500 °C to 700 °C.

scholarly journals Новый механизм реализации омических контактов

2018 ◽  
Vol 52 (1) ◽  
pp. 138
Author(s):  
А.В. Саченко ◽  
А.Е. Беляев ◽  
Р.В. Конакова
Keyword(s):  
Barrier Height ◽  
Ohmic Contacts ◽  
Contact Potential Difference ◽  
Surface States ◽  
Semiconductor Interface ◽  
Contact Potential ◽  
Semiconductor Doping ◽  
Semiconductor Contacts ◽  
Contact Barrier ◽  
Semiconductor Contact

AbstractAnalysis of the contact-barrier height taking into account the distribution of surface states along coordinate x perpendicular to the insulator–semiconductor interface is performed for metal–semiconductor contacts with a dielectric gap. It is shown that taking into account the spatial dependence of the density of surface states at rather high semiconductor doping levels leads to a substantial decrease in the barrier height, which promotes the realization of ohmic contacts. It is established that the smaller the metal–semiconductor contact potential difference ϕ_ ms is, the stronger the effect of barrier-height lowering. If ϕ_ ms is negative, this effect can lead to potential sign reversal, i.e., to the realization of an enrichment layer in the space-charge region of the semiconductor even at a high density of surface states. This in turn promotes the manifestation of an anomalous dependence of the contact resistivity on temperature; the resistivity increases with an increase in temperature.

Low-temperature formation of Mg/n-type 4H-SiC ohmic contacts with atomically flat interface by lowering of Schottky barrier height

2021 ◽  
Author(s):  
Takuma Doi ◽  
Shigehisa Shibayama ◽  
Mitsuo Sakashita ◽  
Kazutoshi Kojima ◽  
Mitsuaki Shimizu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Schottky Barrier ◽  
Barrier Height ◽  
Ohmic Contacts ◽  
Schottky Barrier Height ◽  
Force Microscopy ◽  
Flat Interface ◽  
Low Temperature Annealing ◽  
Atomic Force ◽  
Low Temperature Process

Abstract To obtain an ohmic contact with a flat interface using a low-temperature process, we investigated the behavior of Schottky barrier height (SBH) at the Mg/n-type 4H-SiC interface to low-temperature annealing. Our results revealed that annealing at 200 °C reduced SBH; a low SBH of 0.28 eV was obtained on the lightly doped substrate. Atomic force microscopy measurements revealed negligible increase in the surface roughness after Mg deposition and annealing. Using the low-temperature process, a contact resistivity of 6.5 × 10−5 Ω⋅cm2 was obtained on the heavily doped substrate, which is comparable to Ni/4H-SiC subjected to annealing of above 950 °C.

Calculations of the Specific Resistance of Contacts to III-V Nitride Compounds

1995 ◽  
Vol 395 ◽  
Author(s):  
P.A. Barnes ◽  
X-J Zhang ◽  
M.L. Lovejoy ◽  
T.J. Drummond ◽  
H.P. Hjalmarson ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Barrier Height ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Semiconductor Interface ◽  
Barrier Heights ◽  
Effective Masses ◽  
Specific Contact ◽  
Correct Determination ◽  
Device Applications

ABSTRACTWe present calculations of the specific contact resistance for metals to GaN. Our calculations include a correct determination of the Fermi level taking into account the effect of the degenerate doping levels, required in creating tunneling ohmic contacts. Using a recently reported improved WKB approximation suitable in representing the depletion width at the metal-semiconductor interface, and a two band k-p model for the effective masses, specific contact resistance was determined as a function of doping concentration. The specific contact resistance was calculated using the best data available for barrier heights, effective masses and dielectric coefficients for GaN. Because the barrier height at the metal-semiconductor interface has a very large effect on the contact resistance and the available data is sketchy or uncertain, the effect of varying the barrier height on the calculated specific contact resistance was investigated. Further, since the III-V nitrides are being considered for high temperature device applications, the specific contact resistance was also determined as a function of temperature.

scholarly journals Metal/Semiconductor Barrier Properties of Non-Recessed Ti/Al/Ti and Ta/Al/Ta Ohmic Contacts on AlGaN/GaN Heterostructures

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2655 ◽  
Author(s):  
Spera ◽  
Greco ◽  
Nigro ◽  
Scalese ◽  
Bongiorno ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Barrier Height ◽  
Ohmic Contacts ◽  
Barrier Properties ◽  
Specific Contact Resistance ◽  
Conductive Atomic Force Microscopy ◽  
Force Microscopy ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Thermionic Field Emission

This paper compares the metal/semiconductor barrier height properties of non-recessed Ti/Al/Ti and Ta/Al/Ta contacts on AlGaN/GaN heterostructures. Both contacts exhibited a rectifying behavior after deposition and after annealing at temperatures up to 550 °C. The ohmic behavior was reached after annealing at 600 °C. High-resolution morphological and electrical mapping by conductive atomic force microscopy showed a flat surface for both contacts, with the presence of isolated hillocks, which had no significant impact on the contact resistance. Structural analyses indicated the formation of the Al3Ti and Al3Ta phases upon annealing. Furthermore, a thin interfacial TiN layer was observed in the Ti/Al/Ti samples, which is likely responsible for a lower barrier and a better specific contact resistance (c = 1.6 10−4 Ωcm2) with respect to the Ta/Al/Ta samples (c = 4.0 10−4 Ωcm2). The temperature dependence of the specific contact resistance was described by a thermionic field emission mechanism, determining barrier height values in the range of 0.58–0.63 eV. These results were discussed in terms of the different microstructures of the interfaces in the two systems.

Investigation of Ge, As, and Au Diffusion in Non-Alloyed Epitaxial Au-Ge Ohmic Contacts to n-GaAs Using Secondary Ion Mass Spectroscopy Backside Sputter Depth-Profiling

1991 ◽  
Vol 240 ◽  
Author(s):  
H. S. LEE ◽  
R. T. Lareau ◽  
S. N. Schauer ◽  
R. P. Moerkirk ◽  
K. A. Jones ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Ion Beam ◽  
Depth Profiling ◽  
Depth Resolution ◽  
High Concentration ◽  
Ohmic Behavior ◽  
Preferential Sputtering ◽  
Specific Contact ◽  
Secondary Ion ◽  
Diffusion Profiles

ABSTRACTA SIMS backside sputter depth-profile technique using marker layers is employed to characterize the diffusion profiles of the Ge, As, and Au in the Au-Ge contacts after annealing at 320 C for various times. This technique overcomes difficulties such as ion beam mixing and preferential sputtering and results in high depth resolution measurements since diffusion profiles are measured from low to high concentration. Localized reactions in the form of islands were observed across the surface of the contact after annealing and were composed of Au, Ge, and As, as determined by SIMS imaging and Auger depth profiling. Backside SIMS profiles indicate both Ge and Au diffusion into the GaAs substrate in the isalnd regions. Ohmic behavior was obtained after a 3 hour anneal with a the lowest average specific contact resistivity found to be ∼ 7 × 100−6 Ω- cm2.

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