Environmental and thermal aging of Au/Ni/p-GaN ohmic contacts annealed in air

S. H. Wang, Suzanne E. Mohney, R. Birkhahn

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

In recent years, Au/Ni/p-GaN ohmic contacts annealed in air have been studied extensively because they provide low specific contact resistances and high transparency. In this article we focus on the environmental and thermal degradation that we have observed in these contacts. When the contacts were not protected from the environment, degradation of the contacts always occurred over a period of days, and after sitting 30 days in the laboratory at room temperature, the current-voltage characteristics of the originally ohmic contacts were nonlinear and the contacts were significantly more resistive. To pinpoint the degradation mechanism, samples were stored at room temperature in dry nitrogen, dry oxygen, dry air, air saturated with water vapor, nitrogen gas saturated with water vapor, or vacuum. These experiments revealed that water vapor was the cause of the room temperature degradation. Since no change in the sheet resistance of the p-type GaN was observed upon aging, four point probe measurements and x-ray photoelectron spectroscopy depth profiles were carried out to determine the interaction between water vapor and the p-type NiO present in the annealed contact metallization. The measurements indicated that hydroxyl groups were incorporated in the NiO, leading to a reduction in its conductivity and presumably a decrease in its hole concentration. Aging studies at 200°C further revealed poor thermal stability of the contacts not only in water vapor but also in nitrogen gas and vacuum, and this degradation was again linked to a degradation in the conductivity of the NiO component of the contact metallization.

Original languageEnglish (US)
Pages (from-to)3711-3716
Number of pages6
JournalJournal of Applied Physics
Volume91
Issue number6
DOIs
StatePublished - Mar 15 2002

Fingerprint

electric contacts
water vapor
degradation
air
nitrogen
room temperature
conductivity
vacuum
thermal degradation
contact resistance
gases
x ray spectroscopy
thermal stability
photoelectron spectroscopy
probes
causes
electric potential
oxygen
profiles
interactions

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

@article{b0c8c67e282d48c1b65c85f47bc71b11,
title = "Environmental and thermal aging of Au/Ni/p-GaN ohmic contacts annealed in air",
abstract = "In recent years, Au/Ni/p-GaN ohmic contacts annealed in air have been studied extensively because they provide low specific contact resistances and high transparency. In this article we focus on the environmental and thermal degradation that we have observed in these contacts. When the contacts were not protected from the environment, degradation of the contacts always occurred over a period of days, and after sitting 30 days in the laboratory at room temperature, the current-voltage characteristics of the originally ohmic contacts were nonlinear and the contacts were significantly more resistive. To pinpoint the degradation mechanism, samples were stored at room temperature in dry nitrogen, dry oxygen, dry air, air saturated with water vapor, nitrogen gas saturated with water vapor, or vacuum. These experiments revealed that water vapor was the cause of the room temperature degradation. Since no change in the sheet resistance of the p-type GaN was observed upon aging, four point probe measurements and x-ray photoelectron spectroscopy depth profiles were carried out to determine the interaction between water vapor and the p-type NiO present in the annealed contact metallization. The measurements indicated that hydroxyl groups were incorporated in the NiO, leading to a reduction in its conductivity and presumably a decrease in its hole concentration. Aging studies at 200°C further revealed poor thermal stability of the contacts not only in water vapor but also in nitrogen gas and vacuum, and this degradation was again linked to a degradation in the conductivity of the NiO component of the contact metallization.",
author = "Wang, {S. H.} and Mohney, {Suzanne E.} and R. Birkhahn",
year = "2002",
month = "3",
day = "15",
doi = "10.1063/1.1448885",
language = "English (US)",
volume = "91",
pages = "3711--3716",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "6",

}

Environmental and thermal aging of Au/Ni/p-GaN ohmic contacts annealed in air. / Wang, S. H.; Mohney, Suzanne E.; Birkhahn, R.

In: Journal of Applied Physics, Vol. 91, No. 6, 15.03.2002, p. 3711-3716.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Environmental and thermal aging of Au/Ni/p-GaN ohmic contacts annealed in air

AU - Wang, S. H.

AU - Mohney, Suzanne E.

AU - Birkhahn, R.

PY - 2002/3/15

Y1 - 2002/3/15

N2 - In recent years, Au/Ni/p-GaN ohmic contacts annealed in air have been studied extensively because they provide low specific contact resistances and high transparency. In this article we focus on the environmental and thermal degradation that we have observed in these contacts. When the contacts were not protected from the environment, degradation of the contacts always occurred over a period of days, and after sitting 30 days in the laboratory at room temperature, the current-voltage characteristics of the originally ohmic contacts were nonlinear and the contacts were significantly more resistive. To pinpoint the degradation mechanism, samples were stored at room temperature in dry nitrogen, dry oxygen, dry air, air saturated with water vapor, nitrogen gas saturated with water vapor, or vacuum. These experiments revealed that water vapor was the cause of the room temperature degradation. Since no change in the sheet resistance of the p-type GaN was observed upon aging, four point probe measurements and x-ray photoelectron spectroscopy depth profiles were carried out to determine the interaction between water vapor and the p-type NiO present in the annealed contact metallization. The measurements indicated that hydroxyl groups were incorporated in the NiO, leading to a reduction in its conductivity and presumably a decrease in its hole concentration. Aging studies at 200°C further revealed poor thermal stability of the contacts not only in water vapor but also in nitrogen gas and vacuum, and this degradation was again linked to a degradation in the conductivity of the NiO component of the contact metallization.

AB - In recent years, Au/Ni/p-GaN ohmic contacts annealed in air have been studied extensively because they provide low specific contact resistances and high transparency. In this article we focus on the environmental and thermal degradation that we have observed in these contacts. When the contacts were not protected from the environment, degradation of the contacts always occurred over a period of days, and after sitting 30 days in the laboratory at room temperature, the current-voltage characteristics of the originally ohmic contacts were nonlinear and the contacts were significantly more resistive. To pinpoint the degradation mechanism, samples were stored at room temperature in dry nitrogen, dry oxygen, dry air, air saturated with water vapor, nitrogen gas saturated with water vapor, or vacuum. These experiments revealed that water vapor was the cause of the room temperature degradation. Since no change in the sheet resistance of the p-type GaN was observed upon aging, four point probe measurements and x-ray photoelectron spectroscopy depth profiles were carried out to determine the interaction between water vapor and the p-type NiO present in the annealed contact metallization. The measurements indicated that hydroxyl groups were incorporated in the NiO, leading to a reduction in its conductivity and presumably a decrease in its hole concentration. Aging studies at 200°C further revealed poor thermal stability of the contacts not only in water vapor but also in nitrogen gas and vacuum, and this degradation was again linked to a degradation in the conductivity of the NiO component of the contact metallization.

UR - http://www.scopus.com/inward/record.url?scp=0037087362&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0037087362&partnerID=8YFLogxK

U2 - 10.1063/1.1448885

DO - 10.1063/1.1448885

M3 - Article

AN - SCOPUS:0037087362

VL - 91

SP - 3711

EP - 3716

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 6

ER -