Current noise in semiconductor quantum dots

We have studied the shot-noise characteristics of semiconductor quantum dot s using Keldysh's perturbation theory based on nonequilibrium Green's funct ion techniques, where the electron-electron interaction is well described i n terms of self-energy. We have found that the shot noise at peaks of Coulo mb oscillations decreases sharply to almost zero when the two barriers are equal and increases to almost the full Poisson noise for the dot with highl y 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 stair case, we have found that the shot noise is suppressed over each current ste p 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 abo ut 0.4 and is 0.5 an average for a dot with equal barriers, and for unequal barriers it is always larger than that for equal barriers on an average.