Subterahertz Acoustical Pumping of Electronic Charge in a Resonant Tunneling Device

We demonstrate that controlled subnanosecond bursts of electronic charge can be transferred through a resonant tunneling diode by successive picosecond acoustic pulses. The effect exploits the nonlinear current-voltage characteristics of the device and its asymmetric response to the compressive and tensile components of the strain pulse. This acoustoelectronic pump opens new possibilities for the control of quantum phenomena in nanostructures.

Figure 1

Schematic band diagrams of a double-barrier resonance tunneling diode (RTD) biased near the resonant threshold (a) and the resonant peak (b). (c) The current-voltage characteristic of the device measured for increasing and decreasing the bias voltage. (d) Temporal evolutions of the strain in the middle of the first barrier (top, dotted curve) and of the strain-induced shift between the electron levels in the quantum well and the 2D emitter (bottom, solid curve). The experimental setup is shown schematically in the inset in (d).

Figure 2

The strain-induced current pulses measured at various bias voltages, $V_b$. The corresponding $V_b$ is shown by the dotted lines connecting the measured current pulses with the corresponding point at the $I_0\mathrm{\text{−}}{V}_b$ characteristic presented on the right panel. The time is counted relative to the moment when the pump pulse hits the metal film at the surface opposite to the RTD device.

Figure 3

(a) Strain-induced current pulses measured at pump density $10\mathrm{mJ}/{\mathrm{cm}}^2$ for bias voltages corresponding to the resonant threshold (lower curve), halfway up the resonant peak in ($I_0\mathrm{\text{−}}{V}_b$) (middle curve) and near the peak of the resonance (upper curve). (b) The strain-induced charge transferred through the device due to the action of the strain pulse as a function of pump density. The traces are offset for clarity.

Figure 4

Model calculations. Temporal evolutions of the current changes induced by strain pulses with amplitudes ${\epsilon }_0={10}^{-3}$ (a) and ${\epsilon }_0={10}^{-4}$ (b), calculated when the device is biased at the resonant threshold (lower curves), halfway up the resonant peak in the ($I\mathrm{\text{−}}V$) curve (middle curves) and at the peak of the resonance (upper curves). The strain pulse arrival time to the RTD is set as $t=0$. For comparison with experimental results, note the different time scales in (a) and Fig. 3. (c) The strain-induced charge transferred through the RTD during the action of the strain pulse as a function of strain pulse amplitude for various amounts of detuning between electron levels in the QW and emitter.