Figure 1
Device structure and the electron transport at B = 0 T. (a) Cross section of the fabricated device. The edges of the InAs QW are contacted with sputtered NbTi. (b) Optical image of the device. The region surrounded by the red dash line represents the mesa. (c) dI/dV vs. Vsd at Vtg = 0 V and B = 0 T. dI/dV measured in the range −0.71 mV < Vsd < 0.71 mV is enhanced due to AR. (d) dI/dV vs. Vtg at Vsd = 0 V is shown. The InAs QW is completely depleted by Vtg. (e) dV/dI with dV/dI measured at Vsd = 2.0 mV subtracted as a function of Vsd is shown. The red, blue, and green lines are measured at Vtg = 0, −0.45, and −0.625 V, respectively. The resistance reduction due to AR decreases as Vtg decreases, indicating that Vtg tunes the carrier density of not only the center region of the 2DEG but also region near the junctions. (f) Schematic image of an equivalent circuit to our junction devices. The applied Vsd is divided between the two junctions and the 2DEG.
