Optimization of Ni/Nb Ratio for High-Temperature-Reliable Ni/Nb Silicide Ohmic Contact on 4H-SiC

2019 ◽  
Vol 963 ◽  
pp. 498-501
Author(s):  
Vuong Van Cuong ◽  
Seiji Ishikawa ◽  
Hiroshi Sezaki ◽  
Tomonori Maeda ◽  
Satoshi Yasuno ◽  
...  
Keyword(s):  
High Temperature ◽  
Ohmic Contact ◽  
Contact Resistivity ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
High Concentration ◽  
Transfer Length ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Specific Contact Resistivity

Low specific contact resistivity and high-temperature reliability of the Ni (x)/Nb (100-x) (where x = 25, 50, 75 nm) ohmic contact to 4H-SiC were investigated. After the annealing process at 1000°C for 3 min in N2 ambient, the I-V curves indicated that all the contacts exhibited the ohmic behaviors. Based on the transfer length method, the specific contact resistivity of the contacts were extracted. High concentration of Ni was responsible for low specific contact resistance of the Ni (75)/Nb (25)/4H-SiC sample by the formation of Ni2Si compound after the fabrication process. However, this contact lost the ohmic behavior at low temperature of 150°C. Whereas, both Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC contacts remained the ohmic behavior for 100-hour aging at 400°C. Two-dimensional X-ray diffraction analyses showed that the presence of carbon agglomeration formed at the interface of the Ni (75)/Nb (25)/4H-SiC contact caused the degradation of this sample when being aged at high temperature environment. Meanwhile, higher concentration of Nb in the Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC samples improved the ability to collect the excess carbon atoms and thus enhanced the high temperature reliability of these contacts when operating in high temperature ambient. Considering both low specific contact resistivity and high temperature reliability, the Ni (50)/Nb (50)/4H-SiC contact can be a good candidate for harsh environment applications.

Effect of Au distribution in NiO/Au film on the ohmic contact formation to p-type GaN

2005 ◽  
Vol 20 (2) ◽  
pp. 456-463 ◽  
Author(s):  
Jiin-Long Yang ◽  
J.S. Chen ◽  
S.J. Chang
Keyword(s):  
Electron Microscopy ◽  
Ohmic Contact ◽  
Incident Angle ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Specific Contact ◽  
P Type

The distribution of Au and NiO in NiO/Au ohmic contact on p-type GaN was investigated in this work. Au (5 nm) films were deposited on p-GaN substrates by magnetron sputtering. Some of the Au films were preheated in N2 ambient to agglomerate into semi-connected structure (abbreviated by agg-Au); others were not preheated and remained the continuous (abbreviated by cont-Au). A NiO film (5 nm) was deposited on both types of samples, and all samples were subsequently annealed in N2 ambient at the temperatures ranging from 100 to 500 °C. The surface morphology, phases, and cross-sectional microstructure were investigated by scanning electron microscopy, glancing incident angle x-ray diffraction, and transmission electron microscopy. I-V measurement on the contacts indicates that only the 400 °C annealed NiO/cont-Au/p-GaN sample exhibits ohmic behavior and its specific contact resistance (ρc) is 8.93 × 10−3 Ω cm2. After annealing, Au and NiO contact to GaN individually in the NiO/agg-Au/p-GaN system while the Au and NiO layers become tangled in the NiO/cont-Au/p-GaN system. As a result, the highly tangled NiO-Au structure shall be the key to achieve the ohmic behavior for NiO/cont-Au/p-GaN system.

Microstructure, electrical properties, and thermal stability of Au-based ohmic contacts to p-GaN

1997 ◽  
Vol 12 (9) ◽  
pp. 2249-2254 ◽  
Author(s):  
L. L. Smith ◽  
R. F. Davis ◽  
M. J. Kim ◽  
R. W. Carpenter ◽  
Y. Huang
Keyword(s):  
High Temperature ◽  
Ohmic Contacts ◽  
Microstructural Characterization ◽  
Secondary Phase ◽  
High Resolution Electron Microscopy ◽  
Contact Resistivity ◽  
Cross Sectional ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Specific Contact Resistivity

The work described in this paper is part of a systematic study of ohmic contact strategies for GaN-based semiconductors. Gold contacts exhibited ohmic behavior on p-GaN when annealed at high temperature. The specific contact resistivity (ρc) calculated from TLM measurements on Au/p-GaN contacts was 53 Ω · cm2 after annealing at 800 °C. Multilayer Au/Mg/Au/p-GaN contacts exhibited linear, ohmic current-voltage (I-V) behavior in the as-deposited condition with ρc = 214 Ω · cm2. The specific contact resistivity of the multilayer contact increased significantly after rapid thermal annealing (RTA) through 725 °C. Cross-sectional microstructural characterization of the Au/p-GaN contact system via high-resolution electron microscopy (HREM) revealed that interfacial secondary phase formation occurred during high-temperature treatments, which coincided with the improvement of contact performance. In the as-deposited multilayer Au/Mg/Au/p-GaN contact, the initial 32 nm Au layer was found to be continuous. However, Mg metal was found in direct contact with the GaN in many places in the sample after annealing at 725 °C for 15 s. The resultant increase in contact resistance is believed to be due to the barrier effect increased by the presence of the low work function Mg metal.

scholarly journals Development of an Extreme High Temperature n-Type Ohmic Contact to Silicon Carbide

2012 ◽  
Vol 717-720 ◽  
pp. 841-844 ◽  
Author(s):  
Laura J. Evans ◽  
Robert S. Okojie ◽  
Dorothy Lukco
Keyword(s):  
Heat Treatment ◽  
Silicon Carbide ◽  
Ohmic Contact ◽  
Operating Temperature ◽  
Specific Contact Resistance ◽  
Transfer Length ◽  
Ohmic Behavior ◽  
Contact Metallization ◽  
Extreme High Temperature ◽  
Specific Contact

We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 °C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 Ω-cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 °C while potentially extending operations to 1000 °C.

Investigation of Cu-Ge/Gaas Metal-Semiconductor Interfaces for Low Resistance Ohmic Contacts

1996 ◽  
Vol 448 ◽  
Author(s):  
Serge Oktyabrsky ◽  
M.A. Borek ◽  
M.O. Aboelfotoh ◽  
J. Narayan
Keyword(s):  
Interfacial Layer ◽  
Ohmic Contacts ◽  
High Thermal Stability ◽  
Contact Resistivity ◽  
Polycrystalline Layer ◽  
Ohmic Behavior ◽  
Semiconductor Interfaces ◽  
Transmission Electron ◽  
Specific Contact ◽  
Specific Contact Resistivity

AbstractChemistry and interfacial reactions of the Cu-Ge alloyed ohmic contacts to n-GaAs with extremely low specific contact resistivity (6.5×10-7 Ω·cm2 for n~1017 cm-3) have been investigated by transmission electron microscopy, EDX and SIMS. Unique properties of the contact layers are related to the formation (at Ge concentration above 15 at.%) of a polycrystalline layer of ordered orthorhombic ε1-Cu3Ge phase. Formation of the ε1-phase is believed to be responsible for high thermal stability, interface sharpness and uniform chemical composition. The results suggest that the formation of the ζ- and ε1,-Cu3Ge phases creates a highly Ge-doped n+-GaAs interfacial layer which provides the low contact resistivity. Layers with Ge deficiency to form ζ-phase show nonuniform intermediate layer of hexagonal β-Cu3As phase which grows epitaxially on Ga{111} planes of GaAs. In this case, released Ga diffuses out and dissolves in the alloyed layer stabilizing the ζ-phase which is formed in the structures with average Ge concentration of as low as 5 at.%. These layers also exhibit ohmic behavior.

500℃ high-temperature reliability of Ni/Nb Ohmic contact on n-type 4H-SiC

2021 ◽  
Author(s):  
Vuong Van Cuong ◽  
Tadashi Sato ◽  
Takamichi Miyazaki ◽  
Tetsuya Meguro ◽  
Seiji Ishikawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Ohmic Contact ◽  
Chemical Compounds ◽  
Etching Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Current Voltage ◽  
The Stability

Abstract The reliability of Ni/Nb ohmic contact on n-type 4H-SiC at 500℃ was investigated. The current-voltage characteristics showed that, while the Ni(50)/Nb(50)/4H-SiC sample without applying the CF4:O2 etching process degraded just after 25-hour and lost ohmic behavior after 50-hour aging, the Ni(75)/Nb(25)/4H-SiC contact undergone CF4:O2 surface treatment still showed excellent stability after aging for 100 hours at 500℃. Though X-ray diffraction results indicated that the chemical compounds remained stable during the aging process, transmission electron microscopy showed that there was a redistribution of the chemical compounds at the interface of the contact after 500℃ aging. The depth distribution of the elements and energy dispersive X-ray analyses revealed that the contribution of carbon agglomeration at the interface accounted for the degradation of the sample without applying the etching process. Whereas the well-controlled excess carbon atoms of the contact undergone CF4:O2 treatment ensured the stability of this contact when operating at high-temperature ambient.

The Influence of Contact Composition, Pretreatment, and Annealing Gas on the Ohmic Behavior of Ti/Al-Based Ohmic Contacts to n-Al0.4Ga0.6N

2001 ◽  
Vol 680 ◽  
Author(s):  
K. O. Schweitz ◽  
T. G. Pribicko ◽  
S. E. Mohney ◽  
T. F. Isaacs-Smith ◽  
J. Williams ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Metal Layer ◽  
Active Role ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Group Iii ◽  
Ohmic Behavior ◽  
Annealing Conditions ◽  
Specific Contact ◽  
Group Iii Nitride

ABSTRACTAs the group III nitride semiconductor technology matures, an increasing number of devices are being fabricated with high Al fraction AlGaN. In this study, ohmic behavior is achieved using Ti/Al/Pt/Au contacts to n-Al0.4Ga0.6N, which is the highest Al fraction for which ohmic contact formation has been reported. The effect of contact composition, pretreatment, and annealing conditions is studied by 30 s isochronal annealing experiments between 500°C and 1000°C. A specific contact resistance ρC of (5±3) × 10−5 ωcm2 is obtained using Ti(26 nm)/Al(74 nm)/Pt(50 nm)/Au(50 nm) contacts to n-Al0.4Ga0.6N annealed in N2 at 800°C; however, this value is shown to be artificially high because the metal sheet resistance RM is 4 ω/⊏ causing an artifact in the data analysis. All contacts with ρC < 10−3 ωcm2 exhibit a local minimum in ρC after annealing at 800°C. The observed increase in ρC upon annealing at 850°C and 900°C, however, is not an artifact originating from a change in RM. The top Au layer is found to play an active role in forming ohmic contacts with low ρC, since omitting the Au layer yields an increase in ρC of two orders of magnitude after annealing at 800°C. Furthermore, leaving out the Au layer requires an annealing temperature of 700°C to result in linear I-V curves for currents up to 100 µA, as opposed to 500°C when the Au layer is present. The role of Au is further studied in Ti(26 nm)/Al(74 nm)/Ni(50 nm)/Au(50 nm) contacts, where Rutherford backscattering spectroscopy reveals Ga in the metal layer and/or Au buried deeper than the original semiconductor-metal interface, and x-ray diffraction indicates the formation of new phases to happen concurrently with a decrease in ρC of three orders of magnitude.

Alloying Behavior and Reliabilty of Pt Embedded Metal/n+-GaAs Thin Ohmic Contact System

1996 ◽  
Vol 448 ◽  
Author(s):  
C.Y. Kim ◽  
W.S. Lee ◽  
H.J. Kwon ◽  
Y.W. Jeong ◽  
J.S. Lee ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Integrated Circuit ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Monolithic Microwave Integrated Circuit ◽  
Surface And Interface ◽  
Transmission Line Method ◽  
Specific Contact

AbstractPt embedded ohmic contacts to n+-GaAs (AuGe-800 Å/ Ni-150 Å/Pt-200 Å/Au-500 Å and AuGe-800 Å/Pt-200 Å/Ni-150 Å/Au-500 Å/n+-GaAs) have been developed for the advanced discrete devices and MMIC (monolithic microwave integrated circuit) applications. The specific contact resistance investigated by Transmission Line Method is 1x10-6 Ω cm2. Ohmic contact reliability investigated by thermal storage test at 300 °C under N2 ambient demonstrated nearly the same contact characteristics after 3000 hours. In both systems, X-ray diffraction results and Auger depth profiles show that the good ohmic contact is related to the formation of Au7Ga2, PtAs2, and Ni19Gen12 phases. AuGa compound enhances the creation of Ga vacancies, allowing incorporation of Ge into Ga sites, and PtAs compound is piled up in the middle of AuGa layer to suppress As outdifrusion from GaAs substrate. TEM cross-sectional view indicates that metal/n+-GaAs reaction layer is ∼ 1200 Å beneath GaAs. Surface and interface are very smooth and abrupt in comparison to conventional AuGe/Ni/Au contact.

Piezoresistive Sensitivity and Al Ohmic Contact of Highly Doped Polycrystalline Silicon Nano Thin Films

2011 ◽  
Vol 483 ◽  
pp. 789-793
Author(s):  
Chang Zhi Shi ◽  
Xiao Wei Liu ◽  
Xuan Wu ◽  
Hai Tao Zheng
Keyword(s):  
Thin Films ◽  
Ohmic Contact ◽  
Polycrystalline Silicon ◽  
Depletion Region ◽  
Contact Resistivity ◽  
Gauge Factor ◽  
Piezoresistive Effect ◽  
Specific Contact ◽  
Specific Contact Resistivity ◽  
Polycrystalline Silicon Films

The piezoresistive and ohmic contact properties of polycrystalline silicon nano thin films were investigated in this paper. The polycrystalline silicon films with different thicknesses and doping concentrations were deposited by LPCVD and doped with boron highly, and then the cantilever beam samples were fabricated by photolithography and wet etching. By measuring the gauge factor and specific contact resistivity, the specific contact resistivity of Al contacts can reach 2.4×10-3Ω·cm2 after the alloying at 450 °C for 20 min; the enhanced piezoresistive effect of highly doped polycrystalline silicon nano thin films was discovered. The conclusions indicated that the enhanced piezoresistive sensitivity of PNTFs is due to the modification of depletion region barrier by ultra high doping and film thickness thinning and the enhancement of tunneling piezoresistive effect. The distinct piezoresistive phenomenon of PNTFs could be utilized for the development and fabrication of miniature piezoresistive sensors.

scholarly journals Performance Improvement of GaN Based Laser Diode Using Pd/Ni/Au Metallization Ohmic Contact

Coatings ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 291 ◽  
Author(s):  
Wenjie Wang ◽  
Wuze Xie ◽  
Zejia Deng ◽  
Haojun Yang ◽  
Mingle Liao ◽  
...  
Keyword(s):  
Laser Diode ◽  
Ohmic Contact ◽  
Threshold Current ◽  
Contact Resistivity ◽  
Excellent Thermal Stability ◽  
Barrier Heights ◽  
Ohmic Behavior ◽  
Surface Oxides ◽  
Specific Contact ◽  
Gan Film

We report an investigation of the effects of different metal systems and surface treatment on the contact performance of GaN lasers. We found that multi-element metal alloy and surface chemical treatment are the keys to achieve good ohmic behavior contacts on GaN laser diodes. Pd/Ni/Au contact demonstrates excellent thermal stability and lowest specific contact resistivity in these metal systems. Properly adjusting the thickness of the Pd and Ni layer and pretreating with the KOH solution can further improve the ohmic contact performance. The improved ohmic behavior of the KOH solution pretreated Pd/Ni/Au contact is attributed to removing surface oxides and the reduction of the schottky barrier heights due to the metal Pd has a high work function and the interfacial reactions occurring between the Pd, Ni, Au, and GaN extends into the GaN film. As a result, a low contact resistivity of 1.66 × 10−5 Ω·cm2 can be achieved from Pd(10 nm)/Ni(10 nm)/Au(30 nm) contacts with KOH solution pretreated on top of the laser diode structure. The power of the GaN based laser diode with the Pd/Ni/Au metallization ohmic contact can be enhanced by 1.95 times and the threshold current decreased by 37% compared to that of the conventional ohmic contact Ni/Au.

Ohmic Contact Behavior of Pt/Ni/Au to p-ZnO

2006 ◽  
Vol 928 ◽  
Author(s):  
Ji-Myon Lee ◽  
Kyoung-Kook Kim ◽  
Hitoshi Tampo ◽  
Akimasa Yamada ◽  
Shigeru Niki
Keyword(s):  
Ohmic Contact ◽  
Profile Analysis ◽  
Specific Contact Resistance ◽  
Bandgap Energy ◽  
X Ray Diffraction ◽  
Current Voltage ◽  
Glancing Angle ◽  
Specific Contact ◽  
Current Voltage Characteristics ◽  
Lower Contact

ABSTRACTThe electrical properties of single Pt (30 nm) and Pt (30 nm)/Ni (30nm)/Au(50nm) multilayer contacts on moderately doped p-ZnO (Na = 5.0 × 1017 /−3) were investigated. Although linear current-voltage characteristics were observed for all samples, a sample that was annealed for 1 min at a temperature above 500 °C resulted in an ohmic contact with good characteristics. The best ohmic contact to p-type ZnO was obtained using a Pt/Ni/Au multilayer contact that was annealed at 600 °C for 1 min under a N2 ambient, showing a specific contact resistance Rc of 1.97 × 10−5 Ω cm2. The fundamental mechanisms for the lower contact resistivity of Pt/Ni/Au contacts are discussed based on glancing angle x-ray diffraction results and Auger depth profile analysis of the multilayer alloying process. Furthermore, we fabricated a ZnO p-n homojunction using Pt/Ni/Au and Ti/Au as the p-type and n-type ohmic contact metal, respectively. The threshold voltage was determined to be about 3.7 V, comparable to the bandgap energy of ZnO.

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