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The inherent asymmetry of the electric transport in graphene is attributed toKlein tunneling across barriers defined by $\textit{pn}$-interfaces betweenpositively and negatively charged regions. By combining conductance and shotnoise experiments we determine the main characteristics of the tunnelingbarrier (height and slope) in a high-quality suspended sample with Au/Cr/Aucontacts. We observe an asymmetric resistance $R_{\textrm{odd}}=100-70$$\Omega$ across the Dirac point of the suspended graphene at carrier density$|n_{\rm G}|=0.3-4 \cdot 10^{11}$ cm$^{-2}$, while the Fano factor displays anon-monotonic asymmetry in the range $F_{\textrm{odd}} \sim 0.03 - 0.1$. Ourfindings agree with analytical calculations based on the Dirac equation with atrapezoidal barrier. Comparison between the model and the data yields thebarrier height for tunneling, an estimate of the thickness of the$\textit{pn}$-interface $d < 20$ nm, and the contact region dopingcorresponding to a Fermi level offset of $\sim - 18$ meV. The strength ofpinning of the Fermi level under the metallic contact is characterized in termsof the contact capacitance $C_c=19 \times 10^{-6}$ F/cm$^2$. Additionally, weshow that the gate voltage corresponding to the Dirac point is given by thework function difference between the backgate material and graphene.

Contact doping, Klein tunneling, and asymmetry of shot noise in suspended graphene