Defect evaluation in InGaAs field effect transistors with HfO₂ or Al₂O₃ dielectric

The performance of InGaAs metal oxide semiconductor field effect transistors with Al₂O₃ or HfO₂ as gate oxide is evaluated and compared. The Al₂O₃ transistors show the lowest subthreshold slope and mid gap D_it, however, the HfO₂ transistors reach a higher maximum transconductance (g_max) due to the higher oxide capacitance. Both high-κ dielectrics show a g_m-frequency dispersion due to tunneling into border traps with a negligible activation energy as determined from temperature dependent measurements. The total amount of trapped charge at border traps is lower in the HfO₂ devices. Scaling the HfO₂ thickness further reduces the g_m-frequency dispersion, possibly due to detrapping to the gate electrode.