${\rm In}_{0.53}{\rm Ga}_{0.47}{\rm As}/{\rm GaAs}_{0.5}{\rm Sb}_{0.5}$ Quantum-Well Tunnel-FETs With Tunable Backward Diode Characteristics

Vertical quantum-well (QW) tunnel-FETs are fabricated based on an ultrathin In_0.53Ga_0.47As/GaAs_0.5Sb_0.5 staggered gap (type-II) heterostructure lattice matched to InP. Area-dependent QW-to-QW tunneling current is demonstrated. Devices with HfO₂ high- k gate dielectric (EOT ~ 1.3 nm) exhibit minimum subthreshold swings of 140 mV/decade at 300 K, with an ON-current density of 0.5 μA/μm² at VDD=0.5 V. Sharp negative differential resistance is observed in the output characteristics. For the first time, gate-tunable backward diode characteristics are demonstrated in this material system, with peak curvature coefficient of 30 V^-1 near VDS=0 V. These results show the potential of vertical TFETs in hybrid IC applications.