High Quality Non-Alloyed Pt Ohmic Contacts to P-Type GaN Using Two-Step Surface Treatment

1999 ◽  
Vol 595 ◽  
Author(s):  
Ja-Soon Jang ◽  
Seong-Ju Park ◽  
Tae-Yeon Seong
Keyword(s):  
Surface Treatment ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Transport Mechanisms ◽  
High Quality ◽  
Ammonium Sulfide ◽  
Current Voltage ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type

AbstractTwo-step surface-treatment is introduced to obtain low resistance Pt contacts to ptype GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx]. This is followed by the second step using BOE. The Pt contact, which was treated sequentially using ultrasonically boiled BOE (10 min) and boiled (NH4)2Sx (10 min), produces a specific contact resistance of 3.0 (±3.8)×10-5 Ωcm2. However, the contact, that was simply BOE-treated, yields 3.1 (±1.1)×10-2 Ωcm2. This indicates that the two-step surface treatment is promising technique for obtaining high quality ohmic contacts to p-GaN. Investigation of the electronic transport mechanisms using current-voltage-temperature (I-V-T) data indicates that thermionic field emission is dominant in the surface-treated Pt contacts.

scholarly journals High Quality Non-Alloyed Pt Ohmic Contacts to P-Type GaN Using Two-Step Surface Treatment

2000 ◽  
Vol 5 (S1) ◽  
pp. 521-527
Author(s):  
Ja-Soon Jang ◽  
Seong-Ju Park ◽  
Tae-Yeon Seong
Keyword(s):  
Surface Treatment ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Transport Mechanisms ◽  
High Quality ◽  
Ammonium Sulfide ◽  
Current Voltage ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type

Two-step surface-treatment is introduced to obtain low resistance Pt contacts to p-type GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx]. This is followed by the second step using BOE. The Pt contact, which was treated sequentially using ultrasonically boiled BOE (10 min) and boiled (NH4)2Sx (10 min), produces a specific contact resistance of 3.0 (±3.8)×10−5 Ωcm2. However, the contact, that was simply BOE-treated, yields 3.1 (±1.1)×10−2 Ωcm2. This indicates that the two-step surface treatment is promising technique for obtaining high quality ohmic contacts to p-GaN. Investigation of the electronic transport mechanisms using current-voltage-temperature (I-V-T) data indicates that thermionic field emission is dominant in the surface-treated Pt contacts.

Comparison of Ni/Au, Pd/Au, and Cr/Au Metallizations for Ohmic Contacts to p-GaN

1996 ◽  
Vol 449 ◽  
Author(s):  
J. T. Trexler ◽  
S. J. Pearton ◽  
P. H. Holloway ◽  
M. G. Mier ◽  
K. R. Evans ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Ohmic Contacts ◽  
Thermionic Emission ◽  
Specific Contact Resistance ◽  
Capping Layer ◽  
Dominant Conduction Mechanism ◽  
Current Voltage ◽  
Structural And Electronic Properties ◽  
Specific Contact ◽  
Thermionic Field Emission

ABSTRACTReactions between electron beam evaporated thin films of Ni/Au, Pd/Au, and Cr/Au on p-GaN with a carrier concentration of 9.8 × 1016 cm−3 were investigated in terms of their structural and electronic properties both as-deposited and following heat treatments up to 600°C (furnace anneals) and 900°C (RTA) in a flowing N2 ambient. Auger electron spectroscopy (AES) depth profiles were used to study the interfacial reactions between the contact metals and the p-GaN. The electrical properties were studied using room temperature current-voltage (1-V) measurements and the predominant conduction mechanisms in each contact scheme were determined from temperature dependent I-V measurements. The metallization schemes consisted of a 500 Å interfacial layer of Ni, Pd, or Cr followed by a 1000 Å capping layer of Au. All schemes were shown to be rectifying as-deposited with increased ohmic character upon heat treatment. The Cr/Au contacts became ohmic upon heating to 900°C for 15 seconds while the other schemes remained rectifying with lower breakdown voltages following heat treatment. The specific contact resistance of the Cr/Au contact was measured to be 4.3×10−1 Ωcm2. Both Ni and Cr have been shown to react with the underlying GaN above 400 °C while no evidence of a Pd:GaN reaction was seen. Pd forms a solid solution with the Au capping layer while both Ni and Cr tend to diffuse through the capping layer to the surface. All contacts were shown to have a combination of thermionic emission and thermionic field emission as their dominant conduction mechanism, depending on the magnitude of the applied reverse bias.

Characteristics of Ti/Pt/Au Ohmic Contacts on p-type GaN/AlxGa1-xN Superlattices

1999 ◽  
Vol 595 ◽  
Author(s):  
L. Zhou ◽  
F. Khan ◽  
A.T. Ping ◽  
A. Osinski ◽  
I. Adesida
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Current Voltage ◽  
Specific Contact ◽  
Superlattice Structures ◽  
P Type

AbstractTi/Pt/Au metallization on p-type GaN/AlxGa1-xN (x=0.10 and 0.20) superlattices (SL) were investigated as ohmic contacts. Current-voltage and specific contact resistance measurements indicate enhanced p-type doping in the superlattice structures compared to that in GaN. Ti/Pt/Au is shown to be an effective ohmic metallization scheme on p-type GaN/AlxGa1-xN superlattices. A specific contact resistance of Rc = 4.6×10-4 Ω-cm2 is achieved for unalloyed Ti/Pt/Au on GaN/Al0.2Ga0.8N SL. This is reduced to 1.3×10-4 Ω-cm2 after annealing for 5 minutes at 300 °C.

scholarly journals Ohmic Contacts on p-Type Al-Implanted 4H-SiC Layers after Different Post-Implantation Annealings

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3468 ◽  
Author(s):  
Monia Spera ◽  
Giuseppe Greco ◽  
Domenico Corso ◽  
Salvatore Di Franco ◽  
Andrea Severino ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Device Fabrication ◽  
Electrical Activation ◽  
Specific Contact Resistance ◽  
Emission Model ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type ◽  
Post Implantation

This paper reports on the electrical activation and Ohmic contact properties on p-type Al-implanted silicon carbide (4H-SiC). In particular, the contacts were formed on 4H-SiC-implanted layers, subjected to three different post-implantation annealing processes, at 1675 °C, 1175 °C, and 1825 °C. Under these post-implantation annealing conditions, the electrical activation of the Al dopant species increased from 39% to 56%. The Ti/Al/Ni contacts showed an Ohmic behavior after annealing at 950 °C. The specific contact resistance ρc could be lowered by a factor of 2.6 with the increase of the post-implantation annealing temperature. The result can be useful for application in device fabrication. Moreover, the dependence of ρc on the active acceptor concentration followed the thermionic field emission model, with a barrier height of 0.63 eV.

Study of Ti/Al/Ni Ohmic Contacts to p-Type Implanted 4H-SiC

2018 ◽  
Vol 924 ◽  
pp. 377-380 ◽  
Author(s):  
Marilena Vivona ◽  
Giuseppe Greco ◽  
Corrado Bongiorno ◽  
Salvatore di Franco ◽  
Raffaella Lo Nigro ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Annealing Temperature ◽  
Specific Contact Resistance ◽  
Electrical Characteristics ◽  
Key Factors ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type ◽  
Resistance Value

This work reports on the electrical and microstructural properties of Ti/Al/Ni contacts to p-type implanted 4H-SiC obtained by rapid thermal annealing of a metal stack of Ti (70 nm)/Al (200 nm)/Ni (50 nm). The contact characteristics were monitored at increasing value of the annealing temperature. The Ohmic behavior of the contact, with a specific contact resistance value of 2.3×10-4Ω·cm2, is obtained for an annealing at 950 °C. The structural analyses of the contact, carried out by XRD and TEM, reveal the occurrence of reactions, with the detection of the Al3Ni2and AlTi phases in the upper part of the contact and of an epitaxially oriented TiC layer at the interface. These reactions are considered the key factors in the formation of an Ohmic contact in our annealed Ti/Al/Ni system. The temperature-dependence study of the electrical characteristics reveals a predominant thermionic field emission (TFE) mechanism for the current conduction through the contact, with a barrier height of 0.56 eV.

scholarly journals Thermally Stable Ohmic Contact to p-Type 4H-SiC Based on Ti3SiC2 Phase

2016 ◽  
Vol 858 ◽  
pp. 553-556 ◽  
Author(s):  
Tony Abi-Tannous ◽  
Maher Soueidan ◽  
Gabriel Ferro ◽  
Mihai Lazar ◽  
Christophe Raynaud ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Magnetron Sputtering ◽  
Ohmic Contact ◽  
Room Temperature ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type

In this study, the electrical properties of Ti3SiC2 based ohmic contacts formed on p-type 4H-SiC(0001) 4°-off substrates were studied. The Ti3SiC2 thin films were grown by thermal annealing (from 900°C to 1200°C) of Ti50Al50 layer deposited by magnetron sputtering. XRD analyzes were performed on the samples to further investigate the compounds formed after annealing. Using TLM structures, the Specific Contact Resistance (SCR) at room temperature of all contacts was measured. The temperature dependence (up to 600°C) of the SCR was studied to understand the current mechanisms at the interface and to determine the barrier height value by fitting the experimental results using the thermionic field emission theory. Aging tests showed that Ti3SiC2 based contacts were stable up to 200h at 600°C under Ar.

scholarly journals Investigations on Ni-Ti-Al Ohmic Contacts Obtained on P-Type 4H-SiC

2012 ◽  
Vol 711 ◽  
pp. 169-173 ◽  
Author(s):  
Farah Laariedh ◽  
Mihai Lazar ◽  
Pierre Cremillieu ◽  
Jean Louis Leclercq ◽  
Dominique Planson
Keyword(s):  
Ohmic Contacts ◽  
Secondary Ion Mass Spectrometry ◽  
Rapid Heating ◽  
Specific Contact Resistance ◽  
Transfer Length ◽  
Current Voltage ◽  
Before And After ◽  
Specific Contact ◽  
Lift Off ◽  
P Type

Transfer Length Method (TLM) based-structures were fabricated on 0.8 µm-thick epitaxial p-type Silicon Carbide (4H-SiC) layers. TLM mesas were defined by a 2 µm height using an SF6/O2 reactive ion etching. TLM metal patterns were obtained by a lift-off procedure and electron beam deposition of Ni, Ti, Al and Pt. The patterned samples were annealed in Argon ambient at temperature ranging from 700°C up to 1000°C in a RTA furnace with a rapid heating ramp (up to 50°C/s) to complete the ohmic contact with the p-type SiC layer. Specific contact resistances were extracted from current/voltage measurements. To identify and follow the profile evolution of constituting element in the contacts and at the SiC/contact interface, the ohmic contacts were characterized using Secondary Ion Mass Spectrometry and Energy-Dispersive X-Ray spectroscopy before and after annealing. Ohmic contacts are obtained only for the Ni/Ti/Al and Ni/Ti/Al/Ni stacking layers and not for the Ti/Al/Ti/Ni and Ti/Al/Ti/Pt/Ni compositions. The specific contact resistance of Ni/Ti/Al/Ni stacking layers was observed to decrease from 2.7×10-4 Ω.cm2 at 700°C and 6.3×10-5 Ω.cm2 at 750°C to a minimal value of 1.5×10-5 Ω.cm2 at 800°C. Ohmic contacts are obtained with a reproducibility of 80 %.

scholarly journals Characteristics of Ti/Pt/Au Ohmic Contacts on p-type GaN/AlxGa1−xN Superlattices

2000 ◽  
Vol 5 (S1) ◽  
pp. 514-520
Author(s):  
L. Zhou ◽  
F. Khan ◽  
A.T. Ping ◽  
A. Osinsk ◽  
I. Adesida
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Current Voltage ◽  
Specific Contact ◽  
Superlattice Structures ◽  
P Type

Ti/Pt/Au metallization on p-type GaN/AlxGa1−xN (x=0.10 and 0.20) superlattices (SL) were investigated as ohmic contacts. Current-voltage and specific contact resistance measurements indicate enhanced p-type doping in the superlattice structures compared to that in GaN. Ti/Pt/Au is shown to be an effective ohmic metallization scheme on p-type GaN/AlxGa1−xN superlattices. A specific contact resistance of Rc = 4.6×10−4 ω-cm2 is achieved for unalloyed Ti/Pt/Au on GaN/Al0.2Ga0.8N SL. This is reduced to 1.3×10−4 ω-cm2 after annealing for 5 minutes at 300 °C.

Comparative Study of the Current Transport Mechanisms in Ni2Si Ohmic Contacts on n- and p-Type Implanted 4H-SiC

2014 ◽  
Vol 778-780 ◽  
pp. 665-668 ◽  
Author(s):  
Marilena Vivona ◽  
Giuseppe Greco ◽  
Salvatore di Franco ◽  
Filippo Giannazzo ◽  
Fabrizio Roccaforte ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Ohmic Contacts ◽  
Electrical Characterization ◽  
Nickel Silicide ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type

The knowledge of the temperature behavior of Ohmic contacts is an important issue to understand the device operation. This work reports an electrical characterization as a function of the temperature carried out on nickel silicide (Ni2Si) Ohmic contacts, used both for n-type and p-type implanted 4H-SiC layers. The temperature dependence of the specific contact resistance suggested that a thermionic field emission mechanism dominates the current transport for contacts on p-type material, whereas a current transport by tunneling is likely occurring in the contacts on n-type implanted SiC. Furthermore, from the temperature dependence of the electrical characteristics, the activation energies for Al and P dopants were determined, resulting of 145 meV and 35 meV, respectively. The thermal stability of the electrical parameters has been demonstrated upon a long-term (up to ~100 hours) cycling in the temperature range 200-400°C.

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

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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