Material investigations for improving stability of Au free Ta/Al-based ohmic contacts annealed at low temperature for AlGaN/GaN heterostructures

Publikation: Beitrag in FachzeitschriftForschungsartikelBeigetragenBegutachtung

Beitragende

  • Anthony Calzolaro - , Professur für Nanoelektronik, NaMLab - Nanoelectronic materials laboratory gGmbH (Autor:in)
  • Rico Hentschel - , Technische Universität Dresden (Autor:in)
  • Ifeanyi Francis Edokam - , X-FAB Dresden GmbH and Co. KG (Autor:in)
  • Victor Sizov - , X-FAB Dresden GmbH and Co. KG (Autor:in)
  • Thomas Mikolajick - , Professur für Nanoelektronik, NaMLab - Nanoelectronic materials laboratory gGmbH (Autor:in)
  • Andre Wachowiak - , Technische Universität Dresden (Autor:in)

Abstract

Gold-free Ta/Al-based ohmic contacts fabricated by sputtering on AlGaN/GaN heterostructures and annealed at low temperature were investigated. The presence of a thin AlN spacer layer at the AlGaN/GaN heterojunction is demonstrated to prevent the ohmic contact formation as shown by rectifying behavior after annealing. Ta as an additional capping layer on Al leads to a severe morphology degradation and subsequent deterioration of the metal stack after annealing at 600 °C due to strong Ta-Al alloying verified by transmission electron microscopy. Using the compound metal TiN as capping layer circumvents the alloy formation, thereby making the contacts much more stable under annealing. A low contact resistance of 0.8 Ω mm was obtained using Ta/Al/TiN metal layers annealed at only 500 °C. The nature of the current transport was investigated by analyzing the temperature dependence of the specific contact resistance, which points towards a current path through the AlGaN barrier by thermionic field emission.

Details

OriginalspracheEnglisch
Aufsatznummer075011
FachzeitschriftSemiconductor science and technology
Jahrgang35
Ausgabenummer7
PublikationsstatusVeröffentlicht - Juli 2020
Peer-Review-StatusJa

Externe IDs

ORCID /0000-0003-3814-0378/work/142256207

Schlagworte

Schlagwörter

  • AlGaN/GaN heterostructures, gold-free, High electron mobility transistors, lowerature annealing, ohmic contacts, tantalum/aluminum/tantalum, tantalum/aluminum/titaniumnitride