Performance enhancement of InAsSb QW-MOSFETs with in-situ H2 plasma cleaning for gate stack formation

The measured split capacitance-voltage (CV) characteristics are shown. The combination of an in-situ H₂ plasma cleaned GaSb cap with a scaled 4.5 nm thick HfO₂ gate dielectric results in higher C_ox versus the ex-situ HCl cleaned 1 nm Al₂O₃/10 nm HfO₂ gate stack. Fig. 5 shows the transfer characteristics (I_D-V_G) of the InAs_0.8Sb_0.2 QW-MOSFETs with an L_G=5 μm. The ON current of the long channel MOSFET is 30 μA/μm with a peak G_m of 100 μS/μm and threshold voltage of -0.2V. The SS slope is calculated to be 215 mV/dec. It is evident that the in-situ H₂ plasma clean results in a 35% improvement over similar QW-MOSFET devices that used an ex-situ HCl clean (SS= 350 mV/dec) [1] (Fig. 9). Fig. 5 shows the corresponding output characteristics (I_D-V_D) exhibiting current saturation at low gate voltages. However, external access resistance dominates I_D-V_D characteristics at high V_G. The access resistance was calculated to be R_EXT= 5.8 kΩ-μm (Fig. 7). The effective mobility corrected for access resistance as a function of carrier density is shown in Fig. 8. The in-situ H₂ plasma processed MOSFET exhibits a peak mobility of 4,000 cm²/Vs which represents an increase of 17.5× over Si NMOSFET. In summary, we have demonstrated a 35% improvement in subthreshold slope for InAs_0.8 Sb_0.2 QW-MOSFET by using in-situ H2 plasma to create a high quality interface between GaSb and HfO₂ over the ex-situ cleaned counterpart The resulting InAs _0.8 Sb _0.2 QW-MOSFET shows 17.5x increase in electron mobility over present day silicon MOSFETs.