High-performance enhancement-mode InAlAs/InGaAs HEMTs using non-alloyed ohmic contact and Pt-based buried-gate

In this paper, we demonstrate greatly improved R_S in an E-HEMT structure using non-alloyed ohmic contact and Pt-based buried gate approaches. First, the non-alloyed ohmic contact technique was used to produce very low contact resistance and to provide sharply defined ohmic edges. Second, in the fabrication of our E-HEMT´s, we first intentionally fabricated depletion-mode HEMTs (D-HEMTs). Subsequently, by annealing the sample at 250°C, these D-HEMTs were changed to E-HEMTs as a result of the Pt-InAlAs reaction taking place under the gate electrode, while the channel region between source and gate remained undepleted. This allowed a small R_S to be maintained An excellent transconductance (g_m) of 1170 mS/mm was achieved for an E-HEMT with a 0.5-μm-gate