Sputter-deposited thin-film amorphous $\mathrm{AlN}\text{:}\mathrm{Er}$ ( $1\text{at}\mathrm{.}\%$ ) emits at 554 and $561\mathrm{nm}$ as a result of ${}^2{H}_{11/2}\to {}^4{I}_{15/2}$ and ${}^4{S}_{3/2}\to {}^4{I}_{15/2}$ transitions. $\mathrm{AlN}\text{:}\mathrm{Yb}$ ( $1\text{at}\mathrm{.}\%$ ) gives a weak emission peak at $966\mathrm{nm}$ as a result of ${}^2{F}_{5/2}\to {}^2{F}_{7/2}$ . The codoping of Er and Yb in AlN results in energy transfer from ${\mathrm{Er}}^{+3}$ to ${\mathrm{Yb}}^{+3}$ and enhances the ${\mathrm{Yb}}^{+3}$ emissions by an order of magnitude. Transfer of electrons occurs from the ${}^4{S}_{3/2}$ state of ${\mathrm{Er}}^{+3}$ to the ${}^2{F}_{5/2}$ state of ${\mathrm{Yb}}^{+3}$ . The weak emission from ${\mathrm{Yb}}^{+3}$ , when excited by a $532\mathrm{nm}$ laser in the absence of ${\mathrm{Er}}^{+3}$ , confirms that the luminescence enhancement in ytterbium is due to energy transfer and not to direct green light excitation by the erbium emission. A possibility of population inversion and a four-level laser cavity formation exists in the ${\mathrm{Er}}^{+3}–{\mathrm{Yb}}^{+3}$ system.