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 H
₂
plasma cleaned GaSb cap with a scaled 4.5 nm thick HfO
₂
gate dielectric results in higher C
_ox
versus the ex-situ HCl cleaned 1 nm Al
₂
O
₃
/10 nm HfO
₂
gate stack. Fig. 5 shows the transfer characteristics (I
_D
-V
_G
) of the InAs
_0.8
Sb
_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 H
₂
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 H
₂
plasma processed MOSFET exhibits a peak mobility of 4,000 cm
²
/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 HfO
₂
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.