= Built-in potential
{title2=$V_b$}
The <built-in potential> of a <p-n junction> is the electrostatic potential difference established when carrier diffusion exposes ionized dopants until the opposing drift and diffusion currents balance. The equilibrium <electrochemical potential> is constant even though the <electric potential> and band edges vary. In a nondegenerate homojunction with neutral-edge majority densities $p_p,n_n$, $eV_b=k_BT\log(p_p n_n/n_i^2)$. This is <band bending> within the same material, not necessarily a discontinuous offset of different materials' band edges.
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