Evidence for Radiative Recombination in $\mathrm{Ga}{\mathrm{As}}_{1-x} {\mathrm{P}}_x:\mathrm{N}$ ($0.28\lesssim x\lesssim 0.45$) Involving an Isolated Nitrogen Impurity State Associated with the ${\Gamma }_1$ Minimum

Photoluminescence data for $\mathrm{Ga}{\mathrm{As}}_{1-x}{\mathrm{P}}_x$ alloys implanted with nitrogen are reported for $0.28\lesssim x\lesssim 1.0$ and for N concentrations from ${10}^{16}\lesssim N_{\mathrm{N}}\lesssim {10}^{20}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Evidence is presented of a new excited shallow bound state (${\mathrm{N}}_{\Gamma }$) of the isolated N impurity, coexisting with the tightly bound ground state (${\mathrm{N}}_X$) of this center. The two levels are associated primarily with nonequivalent conduction-band minima.