Inverted order of acceptor and donor levels of monatomic hydrogen in silicon

The acceptor level ${\mathrm{\varepsilon }}_{\mathit{A}}$ of monatomic hydrogen ${(}^2$H) in crystalline silicon has been located at ${\mathrm{\varepsilon }}_{\mathit{A}}$≊${\mathrm{\varepsilon }}_{\mathit{m}}$+0.00 eV, where ${\mathrm{\varepsilon }}_{\mathit{m}}$ is the midgap level, more than 0.3 eV below the recently identified donor level. Thus, hydrogen has a large negative ‘‘effective Coulomb energy.’’ We obtain ${\mathrm{\varepsilon }}_{\mathit{A}}$, via the principle of detailed balance, from separately measured electron emission and capture rates, assuming that the processes ${\mathrm{H}}^{+}$+2${\mathit{e}}^{\mathrm{-}}$⇆${\mathrm{H}}^{\mathrm{-}}$ proceed by a brief residence in the ground state of ${\mathrm{H}}^0$. Such routes seem indicated by ab initio calculations of the energies of ${\mathrm{H}}^{+}$, ${\mathrm{H}}^0$, and ${\mathrm{H}}^{\mathrm{-}}$ for various atomic positions and relaxations.