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(a)-(c) HAADF images recorded in 〈112〉 together with EDX maps of the indicated areas for 2, 8, and 14 min. of InAs growth (samples B, C, and D), respectively. The InAsSb shell is directly visible in the EDX maps, but also due to increased contrast along the core-shell interface for 14 and 8 min. samples. The contrast in the In EDX map for sample B has been enhanced to make the thin shell visible. Scale bars are 100 nm (d) SEM image of a fabricated GaSb/InAs(Sb) core/shell transistor structure.
(a) Transfer characteristics of bare GaSb and core/shell GaSb/InAs NWFETs with different InAs shell thicknesses, corresponding to Samples A, B, C1, and D. (b) Output characteristics of an ambipolar GaSb/InAs NWFET (black curve in part a) from sample C1 for different applied V GS = 0 to 2.5 V (n-branch) and V GS = 0 to −2.5 V (p-branch), in steps of 0.5 V (c) Transfer characteristics and transconductance of a GaSb/InAs NWFET with Al2O3 as the gate-oxide, and with similar p- and n-branch behavior.
(a) I DS vs V GS of a bare-GaSb NWFET for V DS = 10 mV and T = 295 to 40 K. (b) Corresponding I DS − V GS curves for a core/shell NWFET with a thin InAs shell at different temperatures. (c) and (d) Output characteristics of a bare-GaSb and GaSb/InAs core/shell NWFET recorded at T = 295 K for VGS = −2 to 2 V in steps of 0.5 V.
(a) I DS vs V GS of two different ambipolar NWFETs for V DS = 50 mV and T = 4.2 K. (b) Charge oscillations at V DS = 1 mV, and T = 4.2 K for a device with a small effective bandgap, where the transport is tuned from single-hole tunneling, to single-electron tunneling. (c) Calculated energies of the electron ground state in InAs relative to the GaSb valence band maximum, as a function of InAs thickness. A bandgap opens up below a threshold thickness of 5 nm (green vertical line). The red dashed line indicates the GaSb valence band maximum. (d) A schematic description of possible charge configurations in the core and shell under different gate biases. (e) Schematic band diagram of a GaSb/InAs core/shell NW with core and shell diameter of 50 and 60 nm, respectively, and carrier concentration of n = p = 5 × 1017 cm−3.
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