Characterization of AuGe‐ and AuTe‐Based Ohmic Contacts on InAs n‐Channel High Electron Mobility Transistors

Transmission line measurements performed on AlSb/GaSb heterostructure buried InAs n‐channels incorporating AuGe‐ and AuTe‐based ohmic contacts show that the optimum contact resistance for Ni/AuGe/Ni/Au metallization is achieved at 325°C for a 20 s annealing process ( ρ c = 2.3 × 10 − 7 Ω cm 2 , a record low for an AlSb/GaSb structure), whereas only 1.3 × 10 − 6 Ω ‐ cm 2 is obtained for the Ni/AuTe/Ni/Au system optimally annealed at 400°C. Uniform alloyed surface morphology is observed in Ni/AuGe/Ni/Au contacts, while the blistered surface appearance of the Ni/AuTe/Ni/Au system correlates with degraded performance. Measured dc and microwave characteristics of 1 μm gate length InAs n‐channel high electron mobility transistors using AuGe‐ and AuTe‐based source/drain contacts show that ohmic contact quality is critical to device performance.