Thermally stable Ge/Ag/Ni ohmic contact for InAlAs/InGaAs/InP HEMTs

Weifeng Zhao, Seiyon Kim, Jian Zhang, Ilesanmi Adesida

Research output: Contribution to journalArticlepeer-review


Excellent annealed ohmic contacts based on Ge/Ag/Ni metallization have been realized in a temperature range between 385 and 500 °C, with a minimum contact resistance of 0.06 Ω·mm and a specific contact resistivity of 2.62 × 10-7 Ω cm2 obtained at an annealing temperature of 425 °C for 60 s in a rapid thermal annealing (RTA) system. Thermal storage tests at temperatures of 215 and 250°C in a nitrogen ambient showed that the Ge/Ag/Ni based ohmic contacts with an overlay of Ti/Pt/Au had far superior thermal stabilities than the conventional annealed AuGe/Ni ohmic contacts for InAlAs/InGaAs high electron mobility transistors (HEMTs). During the storage test at 215°C, the ohmic contacts showed no degradation after 200 h. At 250°C, the contact resistance value of the Ge/Ag/Ni ohmic contact increased only to a value of 0.1 Ω·mm over a 250-h period. Depletion-mode HEMTs (D-HEMTs) with a gate length of 0.2 μm fabricated using Ge/Ag/Ni ohmic contacts with an overlay of Ti/Pt/Au demonstrated excellent dc and RF characteristics.

Original languageEnglish (US)
Pages (from-to)4-6
Number of pages3
JournalIEEE Electron Device Letters
Issue number1
StatePublished - Jan 1 2006


  • Annealed
  • Ge/Ag/Ni
  • High electron mobility transistors (HEMTs)
  • InAlAs/InGaAs
  • Ohmic contact
  • SiN
  • Storage test
  • Thermal stability

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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