Influence of nickel layer thickness on the magnetic properties and contact resistance of AuGe/Ni/Au Ohmic contacts to GaAs/AlGaAs heterostructures

T. S. Abhilash, Ch Ravi Kumar, G. Rajaram

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)

Abstract

The magnetization of alloyed Ohmic contact film structures of the form AuGe/Ni/Au deposited on a GaAs/AlGaAs heterostructure substrate are reported as functions of Ni-layer thickness and alloying temperature. The observations are correlated with contact resistance and surface morphology studies. It is found that drops in magnetization, due to conversion of Ni to a non-magnetic phase or alloy, begin at anneal temperatures as low as 100 °C for all Ni-layer thicknesses. The conversion is completed at an anneal temperature, T A, that increases with Ni-layer thickness. TA varies from 100-200 °C to 400-430 °C as Ni-layer thickness is varied from 10 to 100 nm for an AuGe (88 : 12 wt%) layer thickness of 100 nm. The electrical contact formation, however, appears to begin at much higher temperatures than 100 °C. Lowest contact resistance (0.05 0.01 Ω mm) is obtained when Ni thickness is about 25 nm for 100 nm AuGe layer thickness, anneal temperature is 400 °C and anneal duration is 60 s. This contact is non-magnetic. Measurements on samples with other AuGe layer thicknesses suggest that the contact resistances are comparable to this optimum value, if the ratio of AuGe layer thickness to that of Ni is ≥4. Increasing the Ni-layer thickness reduces the roughness of annealed contacts, but also increases contact resistance. The magnetic measurements are suggestive of a transformed Ni-layer thickness proportional to the thickness of the underlying AuGe layer. It is proposed that Ni diffuses into AuGe in a concentration limited diffusive mechanism followed by segregation into Ni3Ge.

Original languageEnglish
Article number125104
JournalJournal of Physics D: Applied Physics
Volume42
Issue number12
DOIs
Publication statusPublished - 18 Sep 2009
MoE publication typeA1 Journal article-refereed

Fingerprint

Ohmic contacts
Contact resistance
contact resistance
Nickel
aluminum gallium arsenides
Heterojunctions
electric contacts
Magnetic properties
nickel
magnetic properties
Magnetization
Temperature
Magnetic variables measurement
Alloying
Surface morphology
Surface roughness
gallium arsenide
Substrates
magnetization
temperature

Cite this

@article{583119cdf35f4fd28f5d6f0d936b8e5d,
title = "Influence of nickel layer thickness on the magnetic properties and contact resistance of AuGe/Ni/Au Ohmic contacts to GaAs/AlGaAs heterostructures",
abstract = "The magnetization of alloyed Ohmic contact film structures of the form AuGe/Ni/Au deposited on a GaAs/AlGaAs heterostructure substrate are reported as functions of Ni-layer thickness and alloying temperature. The observations are correlated with contact resistance and surface morphology studies. It is found that drops in magnetization, due to conversion of Ni to a non-magnetic phase or alloy, begin at anneal temperatures as low as 100 °C for all Ni-layer thicknesses. The conversion is completed at an anneal temperature, T A, that increases with Ni-layer thickness. TA varies from 100-200 °C to 400-430 °C as Ni-layer thickness is varied from 10 to 100 nm for an AuGe (88 : 12 wt{\%}) layer thickness of 100 nm. The electrical contact formation, however, appears to begin at much higher temperatures than 100 °C. Lowest contact resistance (0.05 0.01 Ω mm) is obtained when Ni thickness is about 25 nm for 100 nm AuGe layer thickness, anneal temperature is 400 °C and anneal duration is 60 s. This contact is non-magnetic. Measurements on samples with other AuGe layer thicknesses suggest that the contact resistances are comparable to this optimum value, if the ratio of AuGe layer thickness to that of Ni is ≥4. Increasing the Ni-layer thickness reduces the roughness of annealed contacts, but also increases contact resistance. The magnetic measurements are suggestive of a transformed Ni-layer thickness proportional to the thickness of the underlying AuGe layer. It is proposed that Ni diffuses into AuGe in a concentration limited diffusive mechanism followed by segregation into Ni3Ge.",
author = "Abhilash, {T. S.} and Kumar, {Ch Ravi} and G. Rajaram",
year = "2009",
month = "9",
day = "18",
doi = "10.1088/0022-3727/42/12/125104",
language = "English",
volume = "42",
journal = "Journal of Physics D: Applied Physics",
issn = "0022-3727",
publisher = "Institute of Physics IOP",
number = "12",

}

Influence of nickel layer thickness on the magnetic properties and contact resistance of AuGe/Ni/Au Ohmic contacts to GaAs/AlGaAs heterostructures. / Abhilash, T. S.; Kumar, Ch Ravi; Rajaram, G.

In: Journal of Physics D: Applied Physics, Vol. 42, No. 12, 125104, 18.09.2009.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Influence of nickel layer thickness on the magnetic properties and contact resistance of AuGe/Ni/Au Ohmic contacts to GaAs/AlGaAs heterostructures

AU - Abhilash, T. S.

AU - Kumar, Ch Ravi

AU - Rajaram, G.

PY - 2009/9/18

Y1 - 2009/9/18

N2 - The magnetization of alloyed Ohmic contact film structures of the form AuGe/Ni/Au deposited on a GaAs/AlGaAs heterostructure substrate are reported as functions of Ni-layer thickness and alloying temperature. The observations are correlated with contact resistance and surface morphology studies. It is found that drops in magnetization, due to conversion of Ni to a non-magnetic phase or alloy, begin at anneal temperatures as low as 100 °C for all Ni-layer thicknesses. The conversion is completed at an anneal temperature, T A, that increases with Ni-layer thickness. TA varies from 100-200 °C to 400-430 °C as Ni-layer thickness is varied from 10 to 100 nm for an AuGe (88 : 12 wt%) layer thickness of 100 nm. The electrical contact formation, however, appears to begin at much higher temperatures than 100 °C. Lowest contact resistance (0.05 0.01 Ω mm) is obtained when Ni thickness is about 25 nm for 100 nm AuGe layer thickness, anneal temperature is 400 °C and anneal duration is 60 s. This contact is non-magnetic. Measurements on samples with other AuGe layer thicknesses suggest that the contact resistances are comparable to this optimum value, if the ratio of AuGe layer thickness to that of Ni is ≥4. Increasing the Ni-layer thickness reduces the roughness of annealed contacts, but also increases contact resistance. The magnetic measurements are suggestive of a transformed Ni-layer thickness proportional to the thickness of the underlying AuGe layer. It is proposed that Ni diffuses into AuGe in a concentration limited diffusive mechanism followed by segregation into Ni3Ge.

AB - The magnetization of alloyed Ohmic contact film structures of the form AuGe/Ni/Au deposited on a GaAs/AlGaAs heterostructure substrate are reported as functions of Ni-layer thickness and alloying temperature. The observations are correlated with contact resistance and surface morphology studies. It is found that drops in magnetization, due to conversion of Ni to a non-magnetic phase or alloy, begin at anneal temperatures as low as 100 °C for all Ni-layer thicknesses. The conversion is completed at an anneal temperature, T A, that increases with Ni-layer thickness. TA varies from 100-200 °C to 400-430 °C as Ni-layer thickness is varied from 10 to 100 nm for an AuGe (88 : 12 wt%) layer thickness of 100 nm. The electrical contact formation, however, appears to begin at much higher temperatures than 100 °C. Lowest contact resistance (0.05 0.01 Ω mm) is obtained when Ni thickness is about 25 nm for 100 nm AuGe layer thickness, anneal temperature is 400 °C and anneal duration is 60 s. This contact is non-magnetic. Measurements on samples with other AuGe layer thicknesses suggest that the contact resistances are comparable to this optimum value, if the ratio of AuGe layer thickness to that of Ni is ≥4. Increasing the Ni-layer thickness reduces the roughness of annealed contacts, but also increases contact resistance. The magnetic measurements are suggestive of a transformed Ni-layer thickness proportional to the thickness of the underlying AuGe layer. It is proposed that Ni diffuses into AuGe in a concentration limited diffusive mechanism followed by segregation into Ni3Ge.

UR - http://www.scopus.com/inward/record.url?scp=70249099255&partnerID=8YFLogxK

U2 - 10.1088/0022-3727/42/12/125104

DO - 10.1088/0022-3727/42/12/125104

M3 - Article

AN - SCOPUS:70249099255

VL - 42

JO - Journal of Physics D: Applied Physics

JF - Journal of Physics D: Applied Physics

SN - 0022-3727

IS - 12

M1 - 125104

ER -