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Band diagram and Fermi-level movement during MOSFET operation for (a) high-k dielectric/bulk GaSb, (b) high-k dielectric/thick GaSb/InAlSb/InGaSb, and (c) high-k dielectric/ultra-thin GaSb/InAlSb/InGaSb. In both (a) and (b), electrons (ρe) and holes (ρh) at the interface could interact with interface defects. Quantum confinement effect becomes more dominant as the thickness of interfacial GaSb layer scales down as in (c). A dramatic increase of subband energies results in fewer carriers near the interface. Therefore, the interaction between interface traps and carriers is suppressed.
Dependence of the effective bandgap (Egeff) of the GaSb/InAlSb heterostructure on the thickness of the interfacial GaSb layer (TGaSb) in terms of monolayers. When TGaSb is smaller than a few monolayers, the effective bandgap of GaSb/InAlSb approaches that of InAlSb alone.
Capacitance measured on the heterostructure with both (a) p- and (b) n- doped channels. Marginal dispersions have been observed at 200 K, indicating minimal impact of interface traps on the capacitance. (c) Ultra-thin interfacial layer of GaSb can be clearly identified in HR-TEM image.
Measured conductance response for the heterostructure compared to bulk GaSb as the control sample. Biasing condition is set to give near flat-band conditions for both cases. Nearly one order-of-magnitude reduction in conduction peaks is observed for the heterostructure compared to control sample.
Transfer characteristics of both (a) p- and (b) n-channel MOSFETs built on the heterostructure in this work, showing sharp switching behavior. Subthreshold swings are 33 mV/dec and 61 mV/dec for n- and p-channel devices, respectively, close to the thermal limit of ln10 kT/q V/dec.
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