Mechanism of Au-GaAs Reaction and Effects on Ohmic Formation

1988 ◽  
Vol 144 ◽  
Author(s):  
L. Lu-Min Yeh ◽  
P. H. Holloway
Keyword(s):  
Activation Energy ◽  
Electrical Properties ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Kcal Mole ◽  
Au Film ◽  
Size Evolution ◽  
Long Time ◽  
Ohmic Contact Formation

ABSTRACTReactions between Au and GaAs occurs during alloying of Au-based ohmic contacts on GaAs. The reaction and electrical properties of annealed Au/GaAs contacts have both been studied. The extent of the Au-GaAs reactions increased with annealing temperature, incorporated Ga and As into the Au film and left pits on the GaAs surface. The activation energy for these reactions was determined to be 17.6 kcal/mole. Analysis of size evolution of reaction pits on GaAs proved that GaAs regrows at long time annealing. A mixed GaAs dissolution-regrowth mechanism is proposed for annealing temperature and time similar to those used to form alloyed ohmic contacts. Increased surface carrier concentrations resulting from accumulation of dopants near the Au/GaAs interface is proposed to enhance ohmic contact formation.

An Approach to Improving the Morphology and Reliability of n-SiC Ohmic Contacts to SiC Using Second-Metal Contacts

2006 ◽  
Vol 527-529 ◽  
pp. 859-862 ◽  
Author(s):  
Matthew H. Ervin ◽  
Kenneth A. Jones ◽  
Un Chul Lee ◽  
Taniya Das ◽  
M.C. Wood
Keyword(s):  
Electrical Properties ◽  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Chemical Properties ◽  
Physical Contact ◽  
Metal Contacts ◽  
Critical Feature ◽  
Excess Carbon ◽  
Ohmic Contact Formation

While nickel ohmic contacts to n-type silicon carbide have good electrical properties, the physical contact, and therefore the reliability, can be poor. An approach is described for using the good electrical properties of Ni ohmic contacts while using another metal for its desired mechanical, thermal and/or chemical properties. In the present work, once the Ni contacts have been annealed forming nickel silicides and achieving low contact resistance, they are etched off. Removing the primary Ni contacts also eliminates the poor morphology, voids, and at least some of the excess carbon produced by the Ni/SiC reaction. The Ni contacts are then replaced by a second contact metal. This second metal displays low contact resistance as-deposited, indicating that the critical feature responsible for the ohmic contact has not been removed by the primary contact etch. Not only does this approach provide more flexibility for optimizing the contact for a given application, it also provides some insight into the ohmic contact formation mechanism.

Correlation Between the Microstructures and the Electrical Properties of Ni/Au/Te/Au Contacts on n-GaAs

1994 ◽  
Vol 337 ◽  
Author(s):  
X. W. Lin ◽  
J. Watté ◽  
K. Wuyts ◽  
W. Swider ◽  
R.E. Silverans ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electrical Properties ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Structural Evolution ◽  
Reaction Products ◽  
Transmission Electron ◽  
Major Reaction ◽  
Ohmic Contact Formation

ABSTRACTThe structural evolution of Ni/Au/Te/Au contacts on n-GaAs (001) was examined, in correlation with their electrical properties as a function of rapid thermal annealing in the temperature range 350 - 600°C. It was found that heating at temperatures ≥ 550°C results in the formation of ohmic contacts, while contacts annealed at lower temperatures remain nonohmic. Transmission electron microscopy revealed that heating ≥ 450°C leads to extensive reactions between Ni/Au/Te/Au and GaAs and deep spike formation into the GaAs. The major reaction products were identified as NiAs and β-AuGa. Ga2Te3 grains, growing epitaxially on GaAs, were detected only in 550°C annealed samples. Heating to 600°C caused considerable Ga2Te3 loss. Implications of these results concerning the ohmic contact formation mechanism are discussed.

The Microstructure and Electrical Properties of Directly Deposited TiN Ohmic Contacts to Gallium Nitride.

1999 ◽  
Vol 595 ◽  
Author(s):  
P. Ruterana ◽  
G. Nouet ◽  
Th. Kehagias ◽  
Ph. Komninou ◽  
Th. Karakostas ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Electrical Properties ◽  
Film Thickness ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Epitaxial Relationship ◽  
Si Doped ◽  
P Type ◽  
20 Nm

AbstractWhen the stoichiometric TiN was deposited directly on GaN, we obtained columnar TiN grains of 5-20 nm section which cross the whole film thickness and are rotated mostly around the [111] axis. The conventional epitaxial relationship is obtained and no amorphous patches are observed at the interface. The deposition of TiN on Si doped GaN layers lead to the formation of an ohmic contact, whereas we obtain a rectifying contact on p type layers.

scholarly journals The effect of annealing temperature on the structural, optical, and electrical properties of CdS films

2010 ◽  
Vol 25 (1) ◽  
pp. 189-196 ◽  
Author(s):  
Hulya Metin ◽  
Mehmet Ari ◽  
Selma Erat ◽  
Semra Durmuş ◽  
Mehmet Bozoklu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Phase Transformation ◽  
Electrical Properties ◽  
Electronic Transport ◽  
Annealing Temperature ◽  
Optical Band Gap ◽  
Urbach Energy ◽  
Band Gap Energy ◽  
Optical And Electrical Properties ◽  
Gap Energy

Cadmium sulfide (CdS) photocatalyst films were grown on glass by chemical bath deposition (pH 9.4, 70 °C) and then annealed in nitrogen from 423 K to 823 K in steps of 100 K. The XRD crystallite size increases in a sigmoidal manner from 60 nm to 100 nm while the optical band gap energy decreases from 2.42 eV to 2.28 eV. This trend is paralleled by the decreasing Urbach energy, but only up to 623 K, where it increases again. This is the temperature where the Cd effectively surpasses the phase transformation from cubic to hexagonal, and the activation energy for electronic transport drops by a factor of nearly two.

A Comparative Optimization of Electrical Properties and Surface Morphology of Ti/Al/Ta/Au Ohmic Contacts in AlGaN/GaN HEMTs on Si(111), Sapphire, 4H-SiC Substrates

2012 ◽  
Vol 538-541 ◽  
pp. 2207-2210
Author(s):  
Sung Jin Cho ◽  
Cong Wang ◽  
Nam Young Kim
Keyword(s):  
Surface Morphology ◽  
Sapphire Substrate ◽  
Ohmic Contact ◽  
Annealing Time ◽  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Contact Process ◽  
Annealing Temperatures ◽  
Ohmic Resistance ◽  
Gan Hemts

In the process of characterizing AlGaN/GaN HEMTs on Si (111), Sapphire, 4H-SiC substrates, various Rapid Thermal Annealing (RTA) conditions for the Ti/Al/Ta/Au ohmic contact process and the resulting surface analysis have been investigated. In order to achieve a low ohmic contact resistance (RC) and a high quality surface morphology, we tested seven steps (800 °C to 920 °C) annealing temperatures and two steps (15, 30 sec) annealing times. According to these annealing temperatures and times, the optimal ohmic resistance of 3.62 × 10-6 Ohm • cm2 on Si(111) substrate, 9.44 × 10-6 Ohm • cm2 on Sapphire substrate and 1.24 × 10-6 Ohm • cm2 on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively. The surface morphologies of the ohmic contact metallization at different annealing temperatures are measured using an Atomic Force Microscope (AFM). AFM morphology Root Mean Square (RMS) level determines the relationship of the annealing temperature and the annealing time for all of the samples. According to these annealing temperatures and times, the optimal ohmic surface RMS roughness of 13.4 nm on Si(111) substrate, 3.8 nm on Sapphire substrate and 2.9 nm on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively.

Low Resistance Ohmic Contacts Formation and Mechanism of Current Transport Through p-GaN and p-AlGaN

2008 ◽  
Vol 1108 ◽  
Author(s):  
Indra Chary ◽  
Boris Borisov ◽  
Vladimir Kuryatkov ◽  
Yuriy Kudryavtsev ◽  
R Asomoza ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Hole Concentration ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Bilayer Thickness ◽  
Aluminum Oxides ◽  
Mg Doping ◽  
Specific Contact

AbstractWe report the influence of surface treatment, annealing temperature and metal bilayer thickness on the specific contact resistance (ρc) of Au/Ni ohmic contacts to p-GaN and p-AlGaN. Ohmic contact on p-GaN with a hole concentration of 6.5 x 1017 cm-3, shows the lowest ρc of ˜9.2 x 10-6 Ω cm2, when GaN was treated in HCl:H2O (3:1) solution before metal deposition and annealed at 500°C for 10 minutes in 90% N2 and 0% O2 atmosphere. Similar procedure applied on p-AlxGa1-xN (x = 5-7%), with a hole concentration of 2.3 x 1017 cm-3, yields a ρc of 1.8 x 10-4 Ω cm2. An increase is observed in ρc when Mg doping exceeds 4 x 1019 cm-3 in both p-GaN and p-AlGaN. This is attributed to Mg self compensation. This increase is more pronounced in AlGaN which we attribute to the presence of residual native aluminum oxides.

Au/Ge/Pd Ohmic Contacts to n-TYPE InP

1992 ◽  
Vol 260 ◽  
Author(s):  
Ping Jian ◽  
Douglas G. Ivey ◽  
Robert Bruce ◽  
Gordon Knight
Keyword(s):  
Thermal Stability ◽  
Contact Resistance ◽  
Transmission Line ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Microstructural Changes ◽  
Ohmic Behavior ◽  
Quaternary Phase ◽  
Transmission Line Method ◽  
Ohmic Contact Formation

ABSTRACTOhmic contact formation and thermal stability in a Au/Ge/Pd metallization to n-type InP, doped to a level of 1017 cm-3, have been investigated. Contact resistance was measured using a transmission line method, while microstructural changes were examined by means of TEM, EDX, CBED and SAD. Contacts became ohmic after annealing at temperatures ranging from 300°C to 375°C. A minimum contact resistance of 2.5×l0-6 Ω-cm2 was obtained after annealing at 350°C for 320s. The drop in resistance to ohmic behavior corresponded to the decomposition of an epitaxial quaternary phase (Au-Ge-Pd-P). Annealing at 400°C and above resulted in Au10In3 spiking into InP and a break down of contact lateral uniformity, which increased contact resistance.

Effects of Annealing and Different Substrate Materials on Ohmic Contact Property of IGZO Films

2013 ◽  
Vol 423-426 ◽  
pp. 846-851
Author(s):  
Ji Feng Shi
Keyword(s):  
Electrical Properties ◽  
Ohmic Contact ◽  
Annealing Temperature ◽  
Optical And Electrical Properties ◽  
Glass Substrates ◽  
Contact Property ◽  
Suitable Temperature ◽  
Contact Characteristic ◽  
Amorphous Ingazno ◽  
Better Than

Amorphous InGaZnO(a-IGZO) films were deposited on the glass substrates with Al/Mo/ITO films separately using magnetron sputtering and photograph methods,to form resistance structures between a-IGZO films and Al/Mo/ITO films.These samples were annealed in the air and N2 ambience in a series of temperature separately.The results show that regardless of N2 or air ambience,samples annealing at 250 degrade,IGZO films show a good ohmic contact characteristic withAl/Mo/ITOmaterials.And,IGZO films have a better ohmic contact characteristic with ITO/Al than Mo. The transmittance of the IGZO films annealed is better than the transmittance of samples without annealing.And ,the transmittance of samples annealed is rising with the increasing of annealing temperature. Considering the optical and electrical properties of IGZO films, we suggest that 250 centi degrades is a suitable temperature for annealing.

Effect of Annealing Temperature on the Photoactivity of ITO/VO2(M)/Au Film Electrodes for Water Splitting

2020 ◽  
Vol 20 (7) ◽  
pp. 4120-4130 ◽  
Author(s):  
Mohamed Rabia ◽  
Mohamed Shaban ◽  
Badr M. Jibali ◽  
Ahmed A. Abdelkhaliek
Keyword(s):  
Activation Energy ◽  
Water Splitting ◽  
Monoclinic Phase ◽  
Annealing Temperature ◽  
Metastable Phase ◽  
Xrd Analysis ◽  
Optimum Conditions ◽  
Au Film ◽  
Annealing Temperatures ◽  
Monochromatic Illumination

A metastable phase ITO/VO2(B) film was prepared under the optimum conditions using a cyclic potentiometric device. Then, a monoclinic phase ITO/VO2(M) film was prepared from the ITO/VO2(B) film using annealing temperatures from 550 to 750 °C. From the XRD analysis, the crystallinity increases with the annealing temperature from 550 to 750 °C. The ITO/VO2(M) film annealed at 750 °C had the optimum optical and structural properties. Then, three electrodes of ITO/VO2(M)/Au were prepared: electrode (I), electrode (II), and electrode (III) at annealing temperatures of 550, 650, and 750 °C, respectively. The three electrodes were applied to generate hydrogen from H2O and examined using the current–volt (I–V) relationship. Additionally, the incident photon-to-current conversion efficiency (IPCE) under monochromatic illumination was investigated. The electrode showed 4% efficiency at 25 °C and reached 8.1% at 45 °C. Finally, the different thermodynamic parameters, i.e., activation energy (Ea), enthalpy (ΔH*), and entropy (S*), were determined for electrode (III) to be 27.33 kJ mol−1, 124.93 kJmol−1, and 109.66 JKmol−1, respectively.

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