The Role of Ni in the Formation of Low Resistance Ni–Ge–Au Ohmic Contacts to n+ GaAs Heterostructures

1999 ◽  
Vol 14 (4) ◽  
pp. 1261-1271 ◽  
Author(s):  
Nancy E. Lumpkin ◽  
Gregory R. Lumpkin ◽  
Mark G. Blackford
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Wetting Agent ◽  
Dopant Distribution ◽  
Low Resistance ◽  
Ni Content ◽  
Alloy Microstructure

Nickel is a commonly used wetting agent in alloyed Au–Ge ohmic contacts to n-GaAs, resulting in uniformity improvements to the morphology and contact resistance. In order to study the role of Ni in Ni–Ge–Au alloys, we have fabricated samples with varying Ni content and characterized them using electron microbeam techniques. Our data indicate the amount of Ni in the alloy affects the microstructure and composition, the morphology of the metal/GaAs interface, and the amount of GaAs consumed during the alloy reaction. Also, the dopant distribution into the GaAs is heterogeneous depending on the alloy microstructure.

scholarly journals Исследование формирования омических контактов Au/Mo/Ti с пониженным сопротивлением к эпитаксиальным слоям алмаза p-типа

2019 ◽  
Vol 89 (12) ◽  
pp. 1923
Author(s):  
М.Н. Дроздов ◽  
Е.В. Демидов ◽  
Ю.Н. Дроздов ◽  
С.А. Краев ◽  
В.И. Шашкин ◽  
...  
Keyword(s):  
Titanium Carbide ◽  
Contact Resistance ◽  
Ohmic Contacts ◽  
Contact Region ◽  
Effective Diffusion ◽  
Protective Properties ◽  
High Adhesion ◽  
Heavy Doping ◽  
P Type

The formation of ohmic Au/Mo/Ti contacts to epitaxial p-type diamond films is studied. The effect of annealing on the electrical and structural properties of contacts has been investigated. It was shown that during rapid thermal annealing, the outer layer of gold protects the contact system from oxidation up to a temperature of 850°C, unlike the simplified Au/Ti system, which is more common in modern works. In Au/Ti structures without a Mo layer after high-temperature annealing, effective diffusion of titanium into the gold layer occurs, which reduces its protective properties and accelerates the diffusion of oxygen to the boundary with the diamond. Oxidation of the Ti/C contact region blocks the formation of a conductive layer of titanium carbide with high adhesion at the border with diamond. The role of various factors in reducing the contact resistance is compared: annealing for the formation of titanium carbide, heavy doping of diamond with boron atoms, and crystalline perfection of epitaxial diamond substrates. For doped epitaxial films grown on single-sector quality substrates, non-annealed ohmic contacts with a record contact resistance of 4•10<-7> Ω•cm<2> were obtained.

Stable Low Resistance Ohmic Contacts To p-GaN

2001 ◽  
Vol 680 ◽  
Author(s):  
Mi-Ran Park ◽  
Wayne A. Anderson
Keyword(s):  
Contact Resistance ◽  
Photoelectron Spectroscopy ◽  
Ohmic Contacts ◽  
Depth Profiling ◽  
Force Microscopy ◽  
Low Resistance ◽  
Atomic Force ◽  
Current Voltage ◽  
Thermionic Field Emission ◽  
P Type

ABSTRACTStable and low-resistance Ohmic contacts are especially important for laser diodes where high current levels are required. Good contacts are especially difficult on p-type GaN which was the motivation for this study. The GaN was epitaxially grown on (0001) sapphire substrates by MOCVD. Resistivity of this layer was 3.5 Ohm-cm and thickness was 2 microns. After conventional cleaning followed by treatment in boiling HNO3: HCl (1:3), metallization was by thermally evaporating 40 nm Au / 60 nm Ni or 70 nm Au / 55 nm Pd. Heat treatment in O2 + N2 at various temperatures followed, with best results at 600 °C or 700 °C, respectively. Best values of the contact resistance were 1.8×10−4 Ohm-cm2 for Pd/Au and 2.65×10−4 Ohm-cm2 for Ni/Au contacts. After repetitive cycling from room temperature to 600 °C, the Ni contacts were very stable and more stable than the Pd contacts. X-ray photoelectron spectroscopy depth profiling showed the Ni contacts to be NiO followed by Au at the interface for the Ni/Au contacts whereas the Pd/Au contacts exhibited a Pd: Au solid solution. Some contacts were quenched in liquid nitrogen following sintering. These contacts were much more uniform under atomic force microscopy examination and gave a 3 times lower contact resistance with the Ni/Au design. Current-voltage-temperature analysis revealed that conduction was predominantly by thermionic field emission.

Dual Role of Tin Reaction Barrier in Gold-Based Metallization to GaAs

1993 ◽  
Vol 300 ◽  
Author(s):  
A. Piotrowska ◽  
E. Kaminska ◽  
M. Guziewicz ◽  
S. Kwiatkowski ◽  
A. Turos
Keyword(s):  
Magnetron Sputtering ◽  
Contact Resistance ◽  
Ohmic Contact ◽  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Tin Films ◽  
Specific Contact ◽  
Tin Diffusion Barrier

ABSTRACTThe formation of ohmic contacts to p-GaAs based on Au-Zn system comprising a TiN diffusion barrier has been investigated using 2 MeV He+ RBS and the specific contact resistance measurements. It has been proved that TiN films deposited by reactive RF bias magnetron sputtering serves two purposes. First it suppresses the arsenic evaporation and thus confines the reaction between AuZn and GaAs. Second, it prevents intermixing between p-GaAs/Au(Zn) ohmic contact and an overlayer of Au.

Low-Resistance Electrical Contacts to p-Type GaN by Using InxGa1-xN Cap Layers

2001 ◽  
Vol 693 ◽  
Author(s):  
Th. Gessmann ◽  
Y.-L. Li ◽  
J. W. Graff ◽  
E. F. Schubert ◽  
J. K. Sheu
Keyword(s):  
Contact Resistance ◽  
Electric Fields ◽  
Ohmic Contacts ◽  
Electrical Contacts ◽  
Specific Contact Resistance ◽  
Low Resistance ◽  
Transmission Line Method ◽  
Specific Contact ◽  
P Type ◽  
20 Nm

AbstractA novel type of low-resistance ohmic contacts is demonstrated utilizing polarization-induced electric fields in thin p-type InGaN layers on p-type GaN. An increase of the hole tunneling probability through the barrier and a concomitant significant decrease of the specific contact resistance can be attributed to a reduction of the tunneling barrier width in the InGaN capping layers due to the polarization-induced electric fields. The specific contact resistance of Ni (10 nm) / Au (30 nm) contacts deposited on the InGaN capping layers was determined by the transmission line method. Specific contact resistances of 1.2 × 10-2 Ω cm2 and 6 × 10-3 & cm2 were obtained for capping layer thicknesses of 20 nm and 2 nm, respectively.

Low Resistance Ti-Si-C Ohmic Contacts for 4H-SiC Power Devices Using Laser Annealing

2017 ◽  
Vol 897 ◽  
pp. 399-402 ◽  
Author(s):  
Milantha de Silva ◽  
Teruhisa Kawasaki ◽  
Takamaro Kikkawa ◽  
Shinichiro Kuroki
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Laser Annealing ◽  
Electrical Contact ◽  
Nickel Silicide ◽  
Specific Contact Resistance ◽  
Low Resistance ◽  
Specific Contact ◽  
Face Side ◽  
Non Equilibrium

Non-equilibrium laser silicidations for low-resistance ohmic contact to 4H-SiC C-face with Titanium was demonstrated. Ti is one of carbon-interstitial type metals. In a conventional nickel silicide (NiSi) electrode on SiC, a carbon agglomeration at the silicide/SiC interface occurs, and contact resistance becomes larger. For suppressing the carbon agglomeration, in this research, nanoseconds non-equilibrium laser annealing was introduced, and also Ti was introduced to form both silicide and carbide. Ti (75, 100 nm)/SiC and Ni (75, 100 nm)/SiC contacts were formed on C-face side of 4H-SiC substrates. Electrical contact properties were investigated after 40 nanoseconds pulse laser annealing in Ar ambient and rapid thermal annealing. As the result, In the case of laser annealing, the lowest specific contact resistance of 2.4×10-4 Ωcm2 was obtained in Ti (75 nm)/SiC sample in the laser power of 2.5 J/cm2.

Low Resistance Ti5Si3/TiC Ohmic contact on Ion-Implanted n-Type 4H-SiC C Face

2018 ◽  
Vol 924 ◽  
pp. 409-412
Author(s):  
Milantha de Silva ◽  
Teruhisa Kawasaki ◽  
Shinichiro Kuroki
Keyword(s):  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Laser Annealing ◽  
Specific Contact Resistance ◽  
High Concentration ◽  
Low Resistance ◽  
Impurity Doped ◽  
Activation Annealing ◽  
Ion Implanted

Low-resistance Ohmic contact on n+4H-SiC C-face with Titanium was demonstrated. In a conventional NiSi Ohmic contat on n-type 4H-SiC, a carbon agglomeration at the silicide/SiC interface occurs, and contact resistance becomes larger. For suppressing the carbon agglomeration, laser annealing and Ti metal were introduced to form both silicide and carbide. Ti (75 nm)/SiC and Ni (75 nm)/SiC Ohmic contacts were formed on backside C-face of high concentration impurity doped 4H-SiC substrates with and without activation annealing. Electrical properties were investigated after 40 nanoseconds pulse laser annealing in Ar ambient. As the result, the lowest specific contact resistance of 7.9×10-5Ωcm2was obtained in Ti (75 nm)/SiC sample in the case of ion implanted sample at 500°C and with activation annealing at a laser power of 2.2 J/cm2.

Low Resistance Non-Transparent ohmic Pt-contacts on p-GaN

2001 ◽  
Vol 693 ◽  
Author(s):  
Andreas Weimar ◽  
Stefan Bader ◽  
Georg Brüderl ◽  
Volker Kümmler
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Hole Concentration ◽  
Blue Laser ◽  
Specific Contact Resistance ◽  
Low Resistance ◽  
Specific Contact ◽  
Device Operation ◽  
Secondary Ion ◽  
Resistance Value

AbstractThe metal – p-GaN junction for low resistance ohmic contacts is still a challenge to be applied in GaN-based opto electronics as well as in power and high frequency devices. Currently, we try to improve the performance of our blue laser diodes. In order to decrease heat generation during device operation it is necessary to ensure as small contact resistances as possible.In this work, we achieved a specific contact resistance value of RC = 1.8 ± 1.7. 10-5 Ωcm2 for Pt-contacts on MOVPE-grown p-GaN. The Pt-layers were deposited by e-beam and thermally assisted vacuum evaporation after a standard cleaning process. For evaluation of Rc we used optimised circular TLM test patterns defined by photolithography. Best contacts were formed by annealing in Nitrogen athmosphere at 500°C.We also investigated the dependence of the contact resistance on the Mg doping concentration. Therefore p-GaN layers with different Mg-concentrations were grown on SiC-substrates and Pt-contacts were processed. For those samples, we investigated the Mg-concentrations, verified by secondary ion mass spectroscopy (SIMS), the hole concentrations and mobilities in dependence of C(Mg), which we obtained from HALL-measurements, and the contact and sheet resistances, measured by circular TLM measurements.The experiments showed that the optimum Mg-concentration for low contact resistances is higher than 2 1019 cm-3 which was found to provide a maximum hole concentration near 7 1017 cm-3. The influence of self-compensation in p-GaN in bulk and near interfaces will be discussed.

W, WSix and Ti/Al Low Resistance Ohmic Contacts to InGaN, InN and InAlN

1996 ◽  
Vol 421 ◽  
Author(s):  
C.B. Vartuli ◽  
S.J. Pearton ◽  
C.R. Abernathy ◽  
J.D. MacKenzie ◽  
R.J. Shul ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Subsequent Annealing ◽  
Specific Contact Resistance ◽  
Low Resistance ◽  
Specific Contact

AbstractW, WSi0.44 and Ti/Al contacts were examined on n+ In0.65Ga0.35N, InN and In0.75Al0.25N. W was found to produce low specific contact resistance (Qc ˜ 10−7 Ω cm2) ohmic contacts to InGaN, with significant reaction between metal and semiconductor at 900 °C mainly due to out diffusion of In and N. WSix showed an as-deposited Qc of 4×10−7 Ω cm2 but this degraded significantly with subsequent annealing. Ti/Al contacts were stable to Ω 600 °C (Qc, ˜ 4×10−7 Ω cm2 at ≤600 °C). The surfaces of these contacts remain smooth to 800 °C for W and WSix and 650 °C for Ti/Al. InN contacted with W and Ti/Al produced ohmic contacts with Qc ˜ 10−7 Ω cm2 and for WSix Qc ˜ Ω cm2.All remained smooth to ˜ 600 °C, but exhibited significant interdiffusion of In, N, W and Ti respectively at higher temperatures. The contact resistances for all three metallization schemes were ≥ 10−4 Ω.cm2 on InAIN, and degrades with subsequent annealing. The Ti/Al was found to react with the InA1N above 400 °C, causing the contact resistance to increase rapidly. W and WSix proved to be more stable with Qc ˜ 10−2 and 10−3 Ω cm2 up to 650 °C and 700 °C respectively.

In-Based Ohmic Contacts to the Base Layer of GaAs-AlGaAs Heterojunction Bipolar Transistors

1990 ◽  
Vol 181 ◽  
Author(s):  
F. Ren ◽  
S. J. Pearton ◽  
W. S. Hobson ◽  
T. R. Fullowan ◽  
A. B. Emerson ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Heterojunction Bipolar Transistors ◽  
Ohmic Contacts ◽  
Bipolar Transistors ◽  
Base Layer ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Specific Contact ◽  
P Type

ABSTRACTThe use of AuBe-In/Ag/Au p-ohmic contacts for the base layer of GaAs-AIGaAs heterojunction bipolar transistors (HBTs) is described. Annealing at 420°C for 20 sec produces a contact resistivity of 0.095 Ω mm and a specific contact resistance of l.5 × 10-7 Ω cm2, and the surface morphology of the contact is excellent. The role of the silver is as a diffusion barrier to prevent Au spiking into the base layer which could degrade the HBT performance. The presence of the In layer is highly desirable in order to reduce the contact resistance, probably by forming an InGaAs phase at the metal-GaAs interface. Beryllium acts as the p-type dopant, and the top Au layer is used to lower the contact sheet resistance. Current transport through the structure is dominated by tunneling through the barrier due to field emission in the highly doped base layer at p-type doping levels above ∼1019 cm−3

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