Differential conductance in three-dimensional resonant tunneling

We report the results of precision numerical calculations of three-dimensional resonant tunneling. Simple fitting formulas are given which parametrize the dependence of the peak differential conductance $G_{\mathrm{res}}$ and the resonance broadening Γ on the tunnel barrier parameters. The maximum value attained by $G_{\mathrm{res}}$ is universally equal to $e^2$/h.