We study the mutual passivation of shallow donor and isovalent N in GaAs. We find that all the donor impurities, ${\mathrm{Si}}_{\mathrm{Ga}}$, ${\mathrm{Ge}}_{\mathrm{Ga}}$, ${\mathrm{S}}_{\mathrm{As}}$, and ${\mathrm{Se}}_{\mathrm{As}}$, bind to N in $\mathrm{GaAs}:\mathrm{N}$, which has a large N-induced band-gap reduction relative to GaAs. For a group-IV impurity such as Si, the formation of the nearest-neighbor ${\mathrm{Si}}_{\mathrm{Ga}}\mathrm{\text{−}}{\mathrm{N}}_{\mathrm{As}}$ defect complex creates a deep donor level below the conduction band minimum (CBM). The coupling between this defect level with the CBM pushes the CBM upwards, thus restoring the GaAs band gap; the lowering of the defect level relative to the isolated ${\mathrm{Si}}_{\mathrm{Ga}}$ shallow donor level is responsible for the increased electrical resistivity. Therefore, Si and N mutually passivate each other’s electrical and optical activities in GaAs. For a group-VI shallow donor such as S, the binding between ${\mathrm{S}}_{\mathrm{As}}$ and ${\mathrm{N}}_{\mathrm{As}}$ does not form a direct bond; therefore, no mutual passivation exists in the $\mathrm{GaAs}:(\mathrm{S}+\mathrm{N})$ system.

• Received 24 October 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.035505