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 degrees C for a 20 s annealing process (rho(c) = 2.3 x 10(-7) Omega cm(2), a record low for an AlSb/GaSb structure), whereas only 1.3 x 10(-5) Omega-cm(2) is obtained for the Ni/AuTe/Ni/Au system optimally annealed at 400 degrees 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 mu m 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.