High temperature stable WSix ohmic contacts on GaN

S. J. Pearton, S. M. Donovan, C. R. Abernathy, F. Ren, J. C. Zolper, M. W. Cole, A. Zeitouny, M. Eizenberg, R. J. Shul

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

We have sputter-deposited 500-1200 Å thick WSi0.45 metallization onto n+ GaN (n≥1019 cm-3) doped either during MOCVD growth or by direct Si+ ion implantation (5×1015 cm-2, 100 keV) activated by RTA at 1100°C for 30 secs. In the epi samples Rc values of ∼10-14 ω cm2 were obtained, and were stable to ∼1000°C. The annealing treatments up to 600°C had little effect on the WSix/GaN interface, but the beta/-W2N phase formed between 700-800°C, concomitant with a strong reduction (approximately a factor of 2) in near-surface crystalline defects in the GaN. Spiking of the metallization down the threading and misfit dislocations was observed at 800°C, extending >5000 Å in some cases. This can create junction shorting in bipolar or thyristor devices, Rc values of <10-6 ωcm2 were obtained on the implanted samples for 950°C annealing, with values of after 1050°C anneals. The lower Rc values compared to epi samples appear to be a result of the higher peak doping achieved, ∼5×1020 cm-3. We observed wide spreads in Rc values over a wafer surface, with the values on 950°C annealed material ranging from 10-7 to 10-4 ω cm2. There appear to be highly nonuniform doping regions in the GaN, perhaps associated with the high defect density (1010 cm-2) in heteroepitaxial material, and this may contribute to the variations observed. We also believe that near-surface stoichiometry is variable in much of the GaN currently produced due to the relative ease of preferential N2 loss and the common use of HT containing growth (and cool-down) ambients. Finally the ohmic contact behavior of WSix on abrupt and graded composition InxAl1-xN layers has been studied as a function of growth temperature, InN mole fraction x=0.5-1) and post WSix deposition annealing treatment. Rc values in the range 10-3/-10sup-5/ ω cm2 are obtained for auto-doped n+ alloys, with the n-type background being little affected by growth conditions (n∼1020 cm-3). InN is the least temperature-stable alloy (les/700°C), and WSix contact morphology is found to depend strongly on the epi growth conditions.

Original languageEnglish
Title of host publication1998 4th International High Temperature Electronics Conference, HITEC 1998
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages296-300
Number of pages5
ISBN (Print)0780345401, 9780780345409
DOIs
StatePublished - 1998
Externally publishedYes
Event1998 4th International High Temperature Electronics Conference, HITEC 1998 - Allbuquerque, United States
Duration: 14 Jun 199818 Jun 1998

Publication series

Name1998 4th International High Temperature Electronics Conference, HITEC 1998

Conference

Conference1998 4th International High Temperature Electronics Conference, HITEC 1998
Country/TerritoryUnited States
CityAllbuquerque
Period14/06/9818/06/98

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