Ohmic contacts to Si-implanted and un-implanted n-type GaN

ABSTRACTWe report on ohmic contacts to Si-implanted and un-implanted n-type GaN on sapphire. A ring shaped contact design avoids the need to isolate the contact structures by additional implantation or etching. Metal layers of Al and Ti/Al were investigated. On un-implanted GaN, post metalization annealing was performed in an RTA for 30 seconds in N2 at temperatures of 700, 800, and 900°C, A minimum specific contact resistance (rc) of 1.4×10−5 Ω-cm2 was measured for Ti/Al at an annealing temperature of 800°C. Although these values are reasonably low, variations of 95% in specific contact resistance were measured within a 500 µm distance on the wafer. These results are most likely caused by the presence of compensating hydrogen. Specific contact resistance variation was reduced from 95% to 10% by annealing at 900°C prior to metalization. On Si-implanted GaN, un-annealed ohmic contacts were formed with Ti/Al metalization. The implant activation anneal of 1120°C generates nitrogen vacancies that leave the surface heavily n-type, which makes un-annealed ohmic contacts with low contact resistivity possible.

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Improvement of the Specific Contact Resistance on P-Type 4H-SiC by Using a Highly P-Typed Doped 4H-SiC Layer Selectively Grown by VLS Transport

Materials Science Forum ◽

10.4028/www.scientific.net/msf.806.57 ◽

2014 ◽

Vol 806 ◽

pp. 57-60

Author(s):

Nicolas Thierry-Jebali ◽

Arthur Vo-Ha ◽

Davy Carole ◽

Mihai Lazar ◽

Gabriel Ferro ◽

...

Keyword(s):

Contact Resistance ◽

Ohmic Contacts ◽

Schottky Barrier Height ◽

Annealing Temperature ◽

Process Condition ◽

Specific Contact Resistance ◽

High Doping Level ◽

Annealing Temperatures ◽

Specific Contact ◽

P Type

This work reports on the improvement of ohmic contacts made on heavily p-type doped 4H-SiC epitaxial layer selectively grown by Vapor-Liquid-Solid (VLS) transport. Even before any annealing process, the contact is ohmic. This behavior can be explained by the high doping level of the VLS layer (Al concentration > 1020 cm-3) as characterized by SIMS profiling. Upon variation of annealing temperatures, a minimum value of the Specific Contact Resistance (SCR) down to 1.3x10-6 Ω.cm2 has been obtained for both 500 °C and 800 °C annealing temperature. However, a large variation of the SCR was observed for a same process condition. This variation is mainly attributed to a variation of the Schottky Barrier Height.

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Ohmic Contacts to p-Type InGaAs/InP with a Graded Bandgap Heterobarrier

MRS Proceedings ◽

10.1557/proc-318-183 ◽

1993 ◽

Vol 318 ◽

Cited By ~ 5

Author(s):

Patrick W. Leech ◽

Geoffrey K. Reeves

Keyword(s):

Contact Resistance ◽

Ohmic Contacts ◽

Rutherford Backscattering Spectrometry ◽

Specific Contact Resistance ◽

Superlattice Structure ◽

Specific Contact ◽

P Type ◽

Metal Layers ◽

Anneal Temperature ◽

Graded Bandgap

ABSTRACTOhmic contacts to p-type InP with an In0.47Ga0.53As buffer layer and an interposed superlattice of 50 Å In0.47Ga0.53As/ 50 Å InP have been investigated. Initial studies of contacts to In0.47Ga0.53As/ InP without the superlattice structure have shown that Pd/Zn/Pd/Au metallization produced a lower specific contact resistance (pc = 1.1 × 10−4 Ω cm2) than Pd/Ge/Au, and over a wider range of anneal temperature than Au/Zn/Au. The incorporation of the superlattice in the p-In0.47Ga0.53As/ InP structure resulted in Pd/Zn/Pd/Au contacts with pc of 3.2 × 10−5 Ω cm2 as-deposited and 7.5 × 10−6 Ω.cm2 after a 500 °C anneal. The presence of Pd/Zn in the metallization was shown as important in reducing pc. Significant intermixing of the metal layers and In0.47Ga0.53As occured at ≥ 350 °C, as revealed by Rutherford backscattering spectrometry.

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Electrical Properties of (Zn, Mn) Containing Multilayer Metallizations to p-Type InGaAs/InP

MRS Proceedings ◽

10.1557/proc-382-425 ◽

1995 ◽

Vol 382 ◽

Author(s):

Patrick W. Leec ◽

Geoffrey K. Reeves ◽

Wei Zhou

Keyword(s):

Electrical Properties ◽

Contact Resistance ◽

Layer Thickness ◽

Annealing Temperature ◽

Specific Contact Resistance ◽

Annealing Temperatures ◽

Specific Contact ◽

A Minor ◽

P Type ◽

Metal Layers

ABSTRACTThe specific contact resistance, pc, of Au/Zn/Au, Ni/Zn/Ni/Au, Pd/Zn/Pt/Au and Pd/Mln/Sb/Pd/Au contacts to p-In0.47Ga0.53As/ InP has been measured as a function of layer thickness of Zn or Mn. All of the as-deposited contacts were ohmic, with pc = 1−2 × 10−5 Ω cm2. Increasing thickness of the Zn layer above 200 Å in the Au/Zn/Au contacts resulted in a minor decrease in pc while producing no change in the Ni/Zn/Ni/Au metallization. For the as-deposited Pd/Mn/Pd/Au contacts, the value of pc was independent of thickness of the Mn layer but differences in pc emerged at annealing temperatures of ≥ 250°. The analysis of these structures by RBS has shown an extensive intermixing of the metal layers at an annealing temperature of 450 °. In the Pd/Zn/Pt/Au contacts, the value of pc was reduced to a minimum value of 8 × 10−6 Ω cm2 by annealing at a temperature of 500 °. An examination of the Pd/Zn/Pt/Au configuration by RBS has shown that the Pt layer acted as a barrier for the indiffusion of the Au.

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Process Parameters Influence on Specific Contact Resistance (SCR) Value for TiAl Ohmic Contacts on GaN Grown on Sapphire

Materials Science Forum ◽

10.4028/www.scientific.net/msf.615-617.955 ◽

2009 ◽

Vol 615-617 ◽

pp. 955-958 ◽

Cited By ~ 9

Author(s):

Olivier Ménard ◽

Frédéric Cayrel ◽

Emmanuel Collard ◽

Daniel Alquier

Keyword(s):

Contact Resistance ◽

Process Parameters ◽

Ohmic Contacts ◽

Annealing Temperature ◽

Contact Process ◽

Surface Cleaning ◽

Specific Contact Resistance ◽

Process Conditions ◽

Specific Contact ◽

Aln Buffer

In this work, Ti/Al bilayer sputtered ohmic contacts on n-type Gallium Nitride films were studied as a function of process parameters such as Ti thickness, surface cleaning procedure or annealing temperature. Epilayers, with doping concentration of 5.8x1018 at.cm-3, were grown on sapphire using AlN buffer layer. Electrical characterizations were made using circular Transfer Length Method (cTLM) patterns with a four probes equipment. Specific Contact Resistance (SCR) was then extracted for all the process conditions. Our results show that surface treatment is not a critical step in the ohmic contact process while annealing temperature has a larger impact. Finally, SCR values of 1x10-5 Ω.cm2 can be reproducibly achieved, which is of high interest for future devices fabrication using this material.

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Current Transport in Ti/Al/Ni/Au Ohmic Contacts to GaN and AlGaN

Materials Science Forum ◽

10.4028/www.scientific.net/msf.556-557.1027 ◽

2007 ◽

Vol 556-557 ◽

pp. 1027-1030 ◽

Cited By ~ 2

Author(s):

Ferdinando Iucolano ◽

Fabrizio Roccaforte ◽

Filippo Giannazzo ◽

A. Alberti ◽

Vito Raineri

Keyword(s):

Contact Resistance ◽

Field Emission ◽

Ohmic Contacts ◽

Theoretical Models ◽

Specific Contact Resistance ◽

Strong Increase ◽

Current Transport ◽

Electrical Characteristics ◽

Structural And Electrical Properties ◽

Specific Contact

In this work, the structural and electrical properties of Ti/Al/Ni/Au contacts on n-type Gallium Nitride were studied. An ohmic behaviour was observed after annealing above 700°C. The structural analysis showed the formation of an interfacial TiN layer and different phases in the reacted layer (AlNi, AlAu4, Al2Au) upon annealing. The temperature dependence of the specific contact resistance demonstrated that the current transport occurs through thermoionic field emission in the contacts annealed at 600°C, and field emission after annealing at higher temperatures. By fitting the data with theoretical models, a reduction of the Schottky barrier from 1.21eV after annealing at 600°C to 0.81eV at 800°C was demonstrated, together with a strong increase of the carrier concentration at the interface. The reduction of the contact resistance upon annealing was discussed by correlating the structural and electrical characteristics of the contacts.

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Modelling Geometrical Effects of Parasitic and Contact Resistance of FET Devices

MRS Proceedings ◽

10.1557/proc-427-147 ◽

1996 ◽

Vol 427 ◽

Cited By ~ 1

Author(s):

Geoffrey K. Reeves ◽

H. Barry Harrison ◽

Patrick W. Leech

Keyword(s):

Contact Resistance ◽

Material Properties ◽

Ohmic Contacts ◽

Difficult Problem ◽

Specific Contact Resistance ◽

Metal Silicide ◽

Transmission Line Model ◽

Specific Contact ◽

Geometrical Effects ◽

Contact Parameters

AbstractThe continual trend in decreasing the dimensions of semiconductor devices results in a number of technological problems. One of the more significant of these is the increase in contact resistance, Rc. In order to understand and counteract this increase, Rc needs to be quantitatively modelled as a function of the geometrical and material properties of the contact. However the use of multiple semiconductor layers for ohmic contacts makes the modelling and calculation of Rc a more difficult problem. In this paper, a Tri-Layer Transmission Line Model (TLTLM) is used to analyse a MOSFET ohmic contact and gatedrain region. A quantitative assessment of the influence on Rc of important contact parameters such as the metal-silicide specific contact resistance, the silicide-silicon specific contact resistance and the gate-drain length can thus be made. The paper further describes some of the problems that may be encountered in defining Rc when the dimensions of certain types of contact found in planar devices decrease.

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Behavior of W and WSix Contact Metallization on n- and p- Type GaN

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300003252 ◽

1999 ◽

Vol 4 (S1) ◽

pp. 684-690

Author(s):

X. A. Cao ◽

F. Ren ◽

J. R. Lothian ◽

S. J. Pearton ◽

C. R. Abernathy ◽

...

Keyword(s):

Contact Resistance ◽

Annealing Temperature ◽

Specific Contact Resistance ◽

Ohmic Behavior ◽

Contact Metallization ◽

Specific Contact ◽

Heavily Doped ◽

Sputter Deposited ◽

Optimum Annealing Temperature ◽

P Type

Sputter-deposited W-based contacts on p-GaN (NA∼1018 cm−3) display non-ohmic behavior independent of annealing temperature when measured at 25°C. The transition to ohmic behavior occurs above ∼250°C as more of the acceptors become ionized. The optimum annealing temperature is ∼700°C under these conditions. These contacts are much more thermally stable than the conventional Ni/Au metallization, which shows a severely degraded morphology even at 700°C. W-based contacts may be ohmic as-deposited on very heavily doped n-GaN, and the specific contact resistance improves with annealing up to ∼900°C.

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Ni-Al-Ti Ohmic Contacts with Preserved Form Factor and Few 10- 4 Ωcm2 Specific Resistance on 0.1-1 Ωcm p-Type 4H-SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.924.385 ◽

2018 ◽

Vol 924 ◽

pp. 385-388 ◽

Cited By ~ 4

Author(s):

Roberta Nipoti ◽

Maurizio Puzzanghera ◽

Maria Concetta Canino ◽

Giovanna Sozzi ◽

Paolo Fedeli

Keyword(s):

Form Factor ◽

Contact Resistance ◽

Contact Area ◽

Room Temperature ◽

Ohmic Contacts ◽

Specific Resistance ◽

Thickness Ratio ◽

Specific Contact Resistance ◽

Specific Contact ◽

P Type

This study shows that a thin Ni film on Al/Ti/4H-SiC metal pads allows to preserve the pad form factor during a 1000 °C/2 min treatment, provided that the Al and Ti film thicknesses are sufficiently thin. Moreover, by reducing the Al to Ti thickness ratio, droplet formation in the contact area is avoided and a mirror-like appearance is obtained. This optimal contact morphology corresponds to a specific contact resistance of few 10-4Ωcm2at room temperature on p-type 4H-SiC with resistivity in the range 0.1 – 1 Ωcm.

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