Current Noise in Semiconductor Quantum Dots

We have studied the shot-noise characteristics of semiconductor quantum dots using Keldysh's perturbation theory based on nonequilibrium Green's function techniques, where the electron-electron interaction is well described in terms of self-energy. We have found that the shot noise at peaks of Coulomb oscillations decreases sharply to almost zero when the two barriers are equal and increases to almost the full Poisson noise for the dot with highly unequal barriers. We have also found that the Coulomb interaction between electrons in the current-carrying state and the bound state hardly affect the noise characteristics in Coulomb oscillations. As for the Coulomb staircase, we have found that the shot noise is suppressed over each current step and the noise power ratio to the full Poisson noise changes periodically with the current. However, the noise power ratio has a minimum value of about 0.4 and is 0.5 on average for a dot with equal barriers, and for unequal barriers it is always larger than that for equal barriers on an average.