Systematic approach to distinguishing a perturbed host state from an impurity state in a supercell calculation for a doped semiconductor: Using GaP:N as an example

We illustrate a systematic approach for distinguishing a perturbed host state from an impurity state in a supercell calculation for a doped semiconductor, using GaP:N as an example and employing a charge-patching technique based on a first-principles pseudopotential method. For GaP:N, we (1) identify an impuritylike state that is resonant with the conduction band minimum in the dilute doping limit, which provides a qualitative explanation for the peculiar behavior of the Aₓ transition; (2) provide an alternative explanation of a recent finding of the existence of multiple impurity states resonant within the conduction band up to the energy of the Γ point; and (3) show that there exists no impurity state caused by a valley-orbit interaction within a few hundred meV proximity of the N bound state, in contrast to the decades long speculation of the existence of such a state.