Effect of Pd or Pt addition to Ti/Al ohmic contact materials for n-type AlGaN

Murai, S.; Masuda, H.; Koide, Y.; Murakami, Masanori
April 2002
Applied Physics Letters;4/22/2002, Vol. 80 Issue 16, p2934
Academic Journal
Effects of Pd or Pt addition to Ti/Al ohmic contact materials used for n-type Al[sub 0.2]Ga[sub 0.8]N grown on the GaN substrates were studied where Si with 2×10[sup 18] cm[sup -3] were doped in the AlGaN layers. The contact metals were prepared by depositing either by the electron-beam or thermal evaporation technique, and then annealed at high temperatures for 30 s in N[sub 2] atmosphere. It was found that the addition of a small amount of Pd or Pt to the Ti/Al ohmic contact materials reduced the contact resistivities of the Ti/Al contacts. The lowest contact resistivity of 4.1×10[sup -6] Ω cm[sup 2] was obtained in the Ti(20 nm)/Pd(5 nm)/Al(200 nm) contact after annealing at 600 °C (where a slash “/” indicates the deposition sequence). The reduction of the contact resistivities by the Pd or Pt addition was believed to be due to increase in the donor concentration in the AlGaN layers by forming Pd–Ga or Pt–Ga compounds in the contact metals after annealing at elevated temperatures. © 2002 American Institute of Physics.


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