▎ 摘　　要

The conductance and the Fano factor in a graphene sheet in the ballistic regime are calculated. The electrostatic potential in the sheet is modeled by a trapezoid barrier, which allows one to use the exact solution of the Dirac equation in a uniform electric field in the slope areas (the two lateral sides of the trapezoid). Asymmetry with respect to the sign of the gate voltage manifests the difference between the Klein tunneling and the overbarrier transmission. The phase coherence between Klein-tunneling events in the slope areas (p-n transitions) leads to conductance and Fano-factor oscillation at high negative gate voltages. The comparison of the developed theory with the experiment supports the conclusion that the Klein tunneling was revealed experimentally.