Improved Ohmic Contacts to n-Type GaAs, Using Oiboride Diffusion Barriers

1985 ◽  
Vol 54 ◽  
Author(s):  
Joel R. Shappirio ◽  
Robert A. Lux ◽  
John J. Finnegan ◽  
Donald C. Fox ◽  
Joseph H. Kwiatkowski
Keyword(s):  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Diffusion Barriers ◽  
Specific Contact ◽  
Contact Resistivities

ABSTRACTOhmic contacts employing Au/Metal/Au/Ge/Ni (Metal=Ni or. TiB2) to n-type GaAs have been investigated. Alloying of the contacts, performed by both optical (rapid thermal) and strip heater methods, resulted in very low specific contact resistivities for the samples employing the TiB2 diffusion barrier. Such contacts are shown to be stable on aging at 350C for 180 hours.

A Microstructual Analysis of Au/Pd/Ti Ohmic Contacts for GaAs-Based Heterojunction Bipolar Transistors (HJBTs)

1991 ◽  
Vol 240 ◽  
Author(s):  
Bernard M. Henry ◽  
A. E. Staton-Bevan ◽  
V. K. M. Sharma ◽  
M. A. Crouch ◽  
S. S. Gill
Keyword(s):  
Structural Properties ◽  
Heterojunction Bipolar Transistors ◽  
Ohmic Contacts ◽  
Heat Treatments ◽  
Bipolar Transistors ◽  
Contact Resistivity ◽  
Base Region ◽  
Specific Contact ◽  
Specific Contact Resistivity ◽  
Contact Resistivities

ABSTRACTAu/Pd/Ti and Au/Ti/Pd ohmic structures to thin p+-GaAs layers have been investigated for use as contacts to the base region of HJBTs. The Au/Pd/Ti contact system yielded specific contact resistivities at or above 2.8 × 10−5Ω:cm2. Heat treatments up to 8 minutes at 380°C caused only limited interaction between the metallization and the semiconductor. The metal penetrated to a maximum depth of ≃2nm. Specific contact resistivity values less than 10−5Ωcm2 were achieved using the Au/Ti/Pd (400/75/75nm) scheme. The nonalloyed Au/Ti/Pd contact showed the best combination of electrical and structural properties with a contact resistivity value of 9 × 10≃6Ωcm2 and Pd penetration of the GaAs epilayer to a depth of cs30nm.

Reliability Tests of Au-Metallized Ni-Based Ohmic Contacts to 4H-n-SiC with and without Nanocomposite Diffusion Barriers

2010 ◽  
Vol 645-648 ◽  
pp. 737-740 ◽  
Author(s):  
Andrian V. Kuchuk ◽  
M. Guziewicz ◽  
Renata Ratajczak ◽  
Marek Wzorek ◽  
V.P. Kladko ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Diffusion Barriers ◽  
Oxygen Penetration ◽  
Long Time ◽  
Small Change ◽  
The Stability ◽  
Reaction Processes ◽  
Aging In Air

The reliability of Ni2Si/n-SiC ohmic contacts with Au overlayer either without or with Ta-Si-N diffusion barrier was investigated after long-time aging in air at 400oC and rapid thermal annealing in Ar up to 800oC. It is shown that aging of the Au/Ni2Si/n-SiC contacts in air at 400oC resulted in complete degradation due to both oxygen penetration and interdiffusion/reaction processes. In contrast, only a small change in properties was detected on the contacts annealed in Ar at 800°C. The stability of both electrical and structural properties of Au/TaSiN/Ni2Si/n-SiC thermally stressed contacts at different conditions points out their superior thermal stability.

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.

Solid-Phase Ohmic Contacts to GaAs with TiN Diffusion Barriers

1984 ◽  
Vol 37 ◽  
Author(s):  
H. P. Kattelus ◽  
J. L. Tandon ◽  
A. H. Hamdi ◽  
M-A. Nicolet
Keyword(s):  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Solid Phase ◽  
Diffusion Barriers ◽  
Thermally Stable ◽  
Ohmic Behavior ◽  
Tin Film ◽  
The Stability ◽  
P Type

AbstractWe report on contacts to p-type GaAs formed by a GaAs/Pt/TiN/Ag system. Ohmic behavior in this system is believed to be accomplished by the solidstate reaction of Pt with GaAs. This reaction is confined by the TiN film which is thermally stable. In addition, the TiN film acts as an excellent diffusion barrier in preventing the intermixing of the top Ag layer with GaAs or Pt. Contacts formed with such controlled reaction have important implications for the stability of shallow p-n junction devices.

Ti/AlNi/W and Ti/Ni2Si/W Ohmic Contacts to P-Type SiC

2006 ◽  
Vol 527-529 ◽  
pp. 903-906 ◽  
Author(s):  
Bang Hung Tsao ◽  
Jacob Lawson ◽  
James D. Scofield
Keyword(s):  
Ohmic Contacts ◽  
High Vacuum ◽  
Surface Region ◽  
Contact Layer ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Main Observation ◽  
The Stability ◽  
P Type ◽  
Contact Resistivities

AlNi and Ni2Si based ohmic contacts to p-type 4H-SiC have been produced using low energy ion implantation, a Ti contact layer, and sequential anneals. Low resistivities were promoted by degenerately (>1020 cm-3) doping the surface region of 4H-SiC epilayers via Al+ implantation. High acceptor activation and improved surface morphology was achieved by capping the samples with pyrolized photoresist and using a two-step anneal sequence in argon. Ti/AlNi/W and Ti/Ni2Si/W stacks of varying Ti and/or binary layer thickness were compared at varying anneal temperatures. AlNi based samples reliably and repeatedly achieved specific contact resistivities as low as 5.5 x10-5 ohm-cm2 after annealing at temperatures of 700-1000°C. For the Ni2Si samples, resistivities as low 4.5x10-4 ohm-cm2 were reached after annealing between 750 and 1100°C. Similarly, a set of Ti/AlNi/Au samples, with or without Ge as an additional contact layer, were prepared via the same procedures. In this case, specific contact resistivities as low as 5.0 x10-4 ohm-cm2 were achieved after annealing the Ti/AlNi/Au samples between 600 and 700°C for 30 minutes in a dynamic argon atmosphere or under high vacuum. The lowest resistivities were realized using thicker (~ 40 nm) Ti layers. I-V analysis revealed superior linear characteristics for the AlNi system, which also exhibited a more stable microstructure after anneal. SIMS and RBS were used to analyze the stability of the stacks subsequent to thermal treatment. AFM analysis demonstrated the superiority of photoresist capping over alternatives in minimizing surface roughness. Linear ohmic behavior after significantly reduced anneal temperature is the main observation of the present study.

Ohmic Contact to n-GaN with TiN Diffusion Barrier

1996 ◽  
Vol 449 ◽  
Author(s):  
E. Kamińska ◽  
A. Piotrowska ◽  
M. Guziewicz ◽  
S. Kasjaniuk ◽  
A. Barcz ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Ohmic Contact ◽  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Diffusion Barriers ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
Thermally Induced ◽  
X Ray ◽  
Tin Diffusion Barrier

ABSTRACTThe formation of n-GaN/Ti ohmic contacts with TiN diffusion barriers has been investigated by electrical measurements, x-ray diffraction and SIMS. It has been shown that the onset of the ohmic behaviour is associated with the thermally induced phase transformation of Ti into TiN at the GaN/Ti interface. It is suggested that the process is accompanied by an increase in the doping level in the semiconductor subcontact region. The presence of a TiN barrier is found to inhibit excessive decomposition of GaN and to confine the reaction between n-GaN and Ti.

Design and Fabrication of GaN-based Permeable-Base Transistors

2003 ◽  
Vol 798 ◽  
Author(s):  
Jasper S. Cabalu ◽  
Liberty L. Gunter ◽  
Ian Friel ◽  
Anirban Bhattacharyya ◽  
Yuri Fedyunin ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Molecular Beam ◽  
Base Layer ◽  
Transistor Structure ◽  
Collector Current ◽  
Icp Etching ◽  
Device Structures ◽  
Specific Contact ◽  
Bias Range ◽  
Contact Resistivities

ABSTRACTIn this work, we present the first successful fabrication of an etched grooved GaN-based permeable-base transistor structure. Growth of the device structures was done by Molecular Beam Epitaxy (MBE) on thick HVPE GaN quasi-substrates. The fabrication process took advantage of isolations pads via He implantation and SiN deposition, as well as submicron ICP etching of collector fingers patterned via e-beam lithography. SEM of the finished devices shows smooth etched finger structures and base layer surface with finger sidewall angles of ∼85° for 1:1 and 1:3 finger spacing. Specific contact resistivities of ∼ 3 × 10-6 Ω•cm2 for the ohmic contacts were achieved with Ti/Al/Ni/Au metallization scheme. Preliminary DC testing of the devices show a collector current IC = 140 mA/mm at VCE of 5V and VBE of +0.5V. The maximum transconductance gm is ∼111 mS/mm in the measured collector-emitter bias range. These values are comparable, within the measurement tolerance, to physics-based modeling results.

Pt:Ti Diffusion Barrier, Interconnect, and Simultaneous Ohmic Contacts to n- and p-Type 4H-SiC

2018 ◽  
Vol 924 ◽  
pp. 381-384 ◽  
Author(s):  
Robert S. Okojie ◽  
Dorothy Lukco
Keyword(s):  
Diffusion Barrier ◽  
Ohmic Contacts ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Specific Contact Resistance ◽  
Long Term Stability ◽  
Specific Contact ◽  
P Type ◽  
Fabrication Costs

We report the initial results of using co-sputtered Pt:Ti 80:20 at. % composition ratio metallization as a diffusion barrier against gold (Au) and oxygen (O), as an interconnect layer, as well as forming simultaneous ohmic contacts to n-and p-type 4H-SiC. Having a single conductor with such combined multi-functional attributes would appreciably reduce the fabrication costs, processing time and complexity that are inherent in the production of SiC based devices. Auger Electron Spectroscopy, Focused Ion Beam-assisted Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy analyses revealed no Au and O migration to the SiC contact surface and minimal diffusion through the Pt:Ti barrier layer after 15 minutes of exposure at 800 oC in atmosphere, thus offering potential long term stability of the ohmic contacts. Specific contact resistance values of 7 x 10-5 and 7.4 x 10-4 Ω-cm2 were obtained on the n (Nd=7 x 1018 cm-3) and p (Na=2 x 1020 cm-3) -type 4H-SiC, respectively. The resistivity of 75 μΩ-cm was obtained for the Pt:Ti layer that was sandwiched between two SiO2 layers and annealed in pure O ambient up to 900 °C, which offers promise as a high temperature interconnect metallization.

Tantalum-Ruthenium Diffusion Barriers for Contacts to SiC

2006 ◽  
Vol 527-529 ◽  
pp. 883-886 ◽  
Author(s):  
S.H. Wang ◽  
Owen Arnold ◽  
C.M. Eichfeld ◽  
S.E. Mohney ◽  
A.V. Adedeji ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Diffusion Barriers ◽  
Specific Contact ◽  
Pull Tests ◽  
P Type

Tantalum-ruthenium diffusion barriers for contacts to SiC were investigated in this work. Stable specific contact resistances of (2 ± 1) x 10-5 Ω cm2 and (4 ± 2) x 10-5 Ω cm2 were measured on p-type 4H SiC for Al/Ni and Ni ohmic contacts, respectively, when they were beneath Ru-rich Ta-Ru barriers aged at 350 °C for 3000 h in air. Annealed Ni ohmic contacts on n-SiC aged at 350 °C in air for 1000 h (the longest time tested) are also very stable. Pull tests revealed greatly improved adhesion between layers in metallization stacks that contained Ta-Ru barriers in place of previously studied Ta-Ru-N barriers. A 5 nm Ta layer inserted between the Ru-rich Ta-Ru barriers and Au was found to further improve the adhesion of the metallization stacks.

X-ray Microanalysis and High Resolution Imaging of Ge-Au-Ni Metal Layers on Gallium Arsenide

1983 ◽  
Vol 25 ◽  
Author(s):  
D. Fathy ◽  
O. L. Krivanek ◽  
J. C. H. Spence ◽  
W. M. Paulson
Keyword(s):  
High Resolution ◽  
Ohmic Contacts ◽  
High Resolution Imaging ◽  
X Ray ◽  
Specific Contact ◽  
High Resolution Tem ◽  
Order Of Magnitude ◽  
Resolution Imaging ◽  
Contact Resistivities ◽  
Metal Layers

ABSTRACTOhmic contacts to GaAs have been studied using a high resolution TEM, an SEM and a STEM with an energy dispersive x-ray attachment. Two different deposition sequences of the constituent Au-Ge-Ni metals yielded specific contact resistivities that varied by one order of magnitude. Crosssection images of the interface between the GaAs and the metal Au-Ge-Ni layers following alloying showed protrusions at the interface. Contacts with low specific resistivities showed deeper protrusion and also significantly more Ge and Ni in the GaAs.

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