Hydrogenic acceptor state
= Hydrogenic acceptor state
{title2=$E_n=-R_A^*/n^2$}
A shallow acceptor can bind an <electron hole> through the screened <Coulomb potential> of a negatively charged impurity. A scalar <band effective mass> approximation gives a hydrogen-like bound-state ladder. Actual valence-band degeneracy and anisotropy can split levels and limit that approximation.