Investigation of Aluminum and Titanium/Aluminum Contacts to n-Type Gallium Nitride

1996 ◽  
Vol 449 ◽  
Author(s):  
B. P. Luther ◽  
S. E. Mohney ◽  
T. N. Jackson ◽  
M. Asif Khan ◽  
Q. Chen ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Gallium Nitride ◽  
Contact Resistance ◽  
Ohmic Contact ◽  
Intermetallic Phase ◽  
Native Oxide ◽  
Intimate Contact ◽  
Depth Profiles ◽  
Titanium Aluminum ◽  
Ohmic Contact Formation

ABSTRACTWe report on a study of Al and Ti/Al contacts to n-type GaN. Al contacts on n-GaN (7 x l017cm-3) annealed in forming gas at 600°C reached a minimum contact resistivity of 8x10~6Qcm2 and had much better thermal stability than reported by previous researchers. Ti/Al (35nm/l 15nm) contacts on n-GaN (5xl0I7cm~3) had resistivities of 7 x l0"6Qcm2 and 5xl0"6Qcm2 after annealing in Ar at 400°C for 5min and 600°C for 15sec, respectively. Depth profiles of Ti/Al contacts annealed at 400°C showed that low contact resistance was only achieved after Al diffused to the GaN interface. We propose that the mechanism for ohmic contact formation in Ti/Al contacts annealed in the 400-600°C range includes reduction of the native oxide on GaN by Ti and formation of an Al-Ti intermetallic phase in intimate contact with the GaN. Contacts with different Ti/Al layer thicknesses were investigated and those with 50nm/100nm layers had the same low resistance and better stability than 25nm/125nm contacts.

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.

A Thermodynamic Approach to Ohmic Contact Formation to p-GaN

1999 ◽  
Vol 595 ◽  
Author(s):  
Bo Liu ◽  
Mikko H. Ahonen ◽  
Paul H. Holloway
Keyword(s):  
Gallium Nitride ◽  
Contact Resistance ◽  
Point Defect ◽  
Ohmic Contact ◽  
Thermodynamic Activity ◽  
Thermodynamic Approach ◽  
Surface Point ◽  
Near Surface ◽  
Ohmic Contact Formation ◽  
Better Than

AbstractA new ohmic contact scheme for gallium nitride is presented. The use of Nitride-forming metal Over Gallide-forming metal, “NOG”, can modify the thermodynamic activity of N and Ga near the interface. This in turn can modify the near-surface point defect concentrations, particularly the vacancies of Ga and N. The principle of this contact scheme was shown to be consistent with results from Ni/Au, Ni/Zn-Au, Ta/Ti, and Ni/Mg/Ni/Si contacts. In the present study, the “NOG” scheme was used to design Ni/Ti/Au and Ni/Al/Au metallization, and addition of Ti and Al nitride-forming metals to the Ni gallide-forming metal led to lower but still high contact resistance. Ti was shown to be better than Al as the nitride-forming metal based on the decrease of resistance in as deposited contacts. Compared to Ni/Au, four times more current was measured in Ni/Ti/Au contacts to p-GaN after anneal at 300°C for 5min. However the addition of the Ti nitride-forming metal led to lower stability at 500°C.

scholarly journals A Thermodynamic Approach to Ohmic Contact Formation to p-GaN

2000 ◽  
Vol 5 (S1) ◽  
pp. 908-914
Author(s):  
Bo Liu ◽  
Mikko H. Ahonen ◽  
Paul H. Holloway
Keyword(s):  
Gallium Nitride ◽  
Contact Resistance ◽  
Point Defect ◽  
Ohmic Contact ◽  
Thermodynamic Activity ◽  
Thermodynamic Approach ◽  
Surface Point ◽  
Near Surface ◽  
Ohmic Contact Formation ◽  
Better Than

A new ohmic contact scheme for gallium nitride is presented. The use of Nitride-forming metal Over Gallide-forming metal, “NOG”, can modify the thermodynamic activity of N and Ga near the interface. This in turn can modify the near-surface point defect concentrations, particularly the vacancies of Ga and N. The principle of this contact scheme was shown to be consistent with results from Ni/Au, Ni/Zn-Au, Ta/Ti, and Ni/Mg/Ni/Si contacts. In the present study, the “NOG” scheme was used to design Ni/Ti/Au and Ni/Al/Au metallization, and addition of Ti and Al nitride-forming metals to the Ni gallide-forming metal led to lower but still high contact resistance. Ti was shown to be better than Al as the nitride-forming metal based on the decrease of resistance in as deposited contacts. Compared to Ni/Au, four times more current was measured in Ni/Ti/Au contacts to p-GaN after anneal at 300°C for 5min. However the addition of the Ti nitride-forming metal led to lower stability at 500°C.

Ohmic Contact Formation on Silicon-doped Gallium Nitride Epilayers by Low Temperature Annealing

2000 ◽  
Vol 338-342 ◽  
pp. 1619-1619
Author(s):  
L.S. Tan ◽  
A. Raman ◽  
K.M. Ng ◽  
S.J. Chua ◽  
A.T.S. Wee ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Low Temperature ◽  
Ohmic Contact ◽  
Science And Technology ◽  
Contact Formation ◽  
Low Temperature Annealing ◽  
Silicon Doped ◽  
Ohmic Contact Formation ◽  
Double Publication

“removed due to double publication”. The original paper: Journal: Semiconductor Science and Technology Create an alertIssue Volume 15, Number 6 Citation: L S Tan et al 2000 Semicond. Sci. Technol. 15 585 doi: 10.1088/0268-1242/15/6/317 can be accesses at IOP: http://iopscience.iop.org/0268-1242/15/6/317

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.

Low Resistance Ohmic Contact Formation of Ni Silicide on Partially Si Ion Implanted n+ 4H-SiC

2014 ◽  
Vol 778-780 ◽  
pp. 689-692 ◽  
Author(s):  
Milantha de Silva ◽  
Tadashi Sato ◽  
Shinichiro Kuroki ◽  
Takamaro Kikkawa
Keyword(s):  
Contact Resistance ◽  
Ohmic Contact ◽  
Bottom Electrode ◽  
Nickel Silicide ◽  
Line Pattern ◽  
Low Resistance ◽  
Contact Formation ◽  
Ohmic Contact Formation ◽  
Ion Implanted

In this work, a partial amorphization is introduced to form a Nickel silicide ohmic contact for 4H-SiC bottom electrode. In a conventional Nickel silicide electrode, a carbon agglomeration at the silicide/SiC interface has been occured, and contant resistance between Ni silicide and SiC substrate became larger. For the reduction of the contact resistance, the partial amorphization of surface of SiC substrate was introduced. By this partial amorphization, the space position of the carbon agglomeration is controlled, and contact resistance can be reduced. As a result, with an amorphous 100 nm line pattern, a reliable contact resistance of 1.9×10-3Ωcm2was realized.

Ohmic contact formation to bulk and heterostructure gallium nitride family semiconductors

2008 ◽  
Vol 94 (3) ◽  
pp. 633-639 ◽  
Author(s):  
Faiz Rahman ◽  
Sun Xu ◽  
Ian M. Watson ◽  
Dinesh Kumar Baid Mutha ◽  
Richard K. Oxland ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Ohmic Contact ◽  
Contact Formation ◽  
Ohmic Contact Formation

Low Au Content Ohmic Contacts to n-GaAs Incorporating Sputtered Tungsten Oxide

1992 ◽  
Vol 260 ◽  
Author(s):  
Naftali Lustig ◽  
R. G. Schad ◽  
A. Fleischman
Keyword(s):  
Electron Beam ◽  
Melting Point ◽  
Contact Resistance ◽  
Gaas Substrate ◽  
Ohmic Contacts ◽  
High Melting ◽  
Low Oxygen ◽  
High Melting Point ◽  
Depth Profiles ◽  
Ohmic Contact Formation

ABSTRACTElectron-beam (e-beam) evaporated low Au content NiGe(Au)W ohmic contacts with a contact resistance (Rc) as low as 0.15 Ω-mra have been reported. Due to the high melting point of W it is desirable to deposit this layer by means other than e-beam evaporation. However, the use of nearly oxygen-free sputtered W, yields contact resistances in excess of 0.7 Ω-mm. By replacing the sputtered W by a reactively sputtered metallic W oxide, containing ∼25 at. % oxygen, the low contact resistance (Rc < 0.15 Ω-mm) is restored. Contacts employing a reactively sputtered W nitride in place of W oxide also yield high Rc's (∼0.75 Ω-mm). Auger depth profiles of the reacted contacts show a significant outdiffusion of Ga from the GaAs substrate in the presence the oxygenated W but not in the low oxygen and the W nitride contacts. These results and the fact that our previously reported e-beam evaporated W contacts also contain ∼25 at. % oxygen, suggest an oxygen assisted ohmic contact formation mechanism.

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