Single-Dot Spectroscopy via Elastic Single-Electron Tunneling through a Pair of Coupled Quantum Dots

We study the electronic structure of a single self-assembled InAs quantum dot by probing elastic single-electron tunneling through a single pair of weakly coupled dots. In the region below pinch-off voltage, the nonlinear threshold voltage behavior provides electronic addition energies exactly as the linear, Coulomb blockade oscillation does. By analyzing it, we identify the $s$ and the $p$ shell addition spectrum for up to six electrons in the single InAs dot, i.e., one of the coupled dots. The evolution of the shell addition spectrum with magnetic field provides Fock-Darwin spectra of the $s$ and $p$ shells.

Figure 1

Schematic illustration of the cross section of the submicron size single-electron transistor used for the experiment and (b) color log-scale plot of $dI/dV$ as a function of $V_{\mathrm{S}\mathrm{D}}$ and $V_G$ close to $V_{\mathrm{S}\mathrm{D}}=0\mathrm{V}$.

Figure 2

Color log-scale plot of $dI/dV$ as a function of $V_{\mathrm{S}\mathrm{D}}$ and $V_G$ in wider $V_{\mathrm{S}\mathrm{D}}$ range and configurations of energy-level diagram corresponding to points ($A$) to ($F$). The inset is calculated $dI/dV$ plot using a simple constant interaction model.

Figure 3

(a) The magnetic field dependence of the position of the $s$ shell VLs ($S_1$ and $S_2$), (b) that of $p$ shell VLs ($P_1$ to $P_4$), and (c) Fock-Darwin states with $\hslash {\omega }_0=15\mathrm{m}\mathrm{e}\mathrm{V}$.