Figure 1: Sample, pump mechanism and gate drive waveforms.
From: Towards a quantum representation of the ampere using single electron pumps
(a) Scanning electron microscope image of a pump similar to the one used in this study. The etched 2-DEG channel runs from left to right, and the two metallic gates (light grey in the image) cross the channel. Scale bar indicates 1 μm. (b) Schematic diagrams of the potential along the channel during four phases of the pump cycle: (1) loading, (2) back-tunneling, (3) trapping and (4) ejection. One cycle transports an electron from the left (source) to the right (drain) lead. (c,d) The two types of gate drive waveforms VRF(t) used in this study: sine waves (c) and shaped pulses (d). Numbered points approximately indicate the corresponding stages in the pump cycle shown in panel (b). In panel (d), the black line shows the pulse shape programmed into the AWG, and the red line shows the actual waveform measured with a fast sampling oscilloscope after passing through a coaxial line similar to the one in the cryogenic measurement probe. The dotted line shows a sine wave of frequency f/5.
