Fano resonances in current-voltage characteristics of nanowires with embedded quantum dots

The electron transport has been studied in a nanowire with a quantum dot (QD) embedded between two barriers, i.e., in a quasi-one-dimensional resonant tunneling diode (RTD). The current-voltage characteristics of the RTD have been calculated taking into account the smoothness of the QD/barrier interfaces and the presence of spacers separating the barriers from the contacts. We have found that the application of narrow spacers essentially modifies the shape of the resonant current peak. The resonant peak possesses the symmetric shape for wide spacers and becomes asymmetric acquiring the Fano resonance shape for sufficiently narrow spacers. The results of calculations agree well with the experimental data for the resonance tunneling in the InP/InAs/InP nanowire.

Figure 1

(Color online) Potential profile in the nanodevice with voltage $V$ applied between the left and right contacts. The QD of size $w$ is defined by two potential barriers of thickness $b$. $E_0$ and $E_1$ are the energy levels of quasibound electron states, $s$ is the width of spacer, $E_c^l$ $\left(E_c^r\right)$ corresponds to the conduction-band bottom of the left (right) contact, and $E_F$ is the Fermi energy. Inset: electron potential energy $U$ as a function of $z$ for $V=0$ and for different values of parameter $p$.

Figure 2

(Color online) Transmission coefficient $T$ as a function of incident electron energy $E$ (left panels) and current $I$ as a function of bias voltage $V$ (right panels) for different widths $s$ of the spacers. In the left panels, the successive transmission peaks (from left to right) correspond to $V=0\text{mV}$, 20 mV, 40 mV, 60mV, and 80 mV, respectively, and the solid curve connecting the maxima of $T$ serves a guide to an eye. These results have been obtained for $R=2.06\text{nm}$, $p=6$, and $I_0=77.48\text{nA}$. $a$ is the lattice constant of InAs. In the right panels, the symmetric peak obtained for $s=1000a$ (a) is plotted by the dashed curve in parts (b), (c), and (d).

Figure 3

(Color online) Parameter $q$ [Eq. (6)] describing the asymmetry of the resonant current peak as a function [Eq. (7)] of width $s$ of the spacers for different widths $w$ of the potential well.

Figure 4

(Color online) Calculated (solid, blue curve) and measured (dotted curve) current-voltage characteristics for InAs/InP resonant tunneling diode. The calculated maximal value of current has been adjusted to the experimental value.