Intense ultraviolet cathodoluminescence at 318 nm from Gd3+-doped AlN

We present investigations of Gd-implanted aluminum nitride, studied with cathodoluminescence (CL) as well as time-resolved CL in the temperature range 12–300 K. Luminescence due to intra-4f electron transitions of ${\mathrm{Gd}}^{\text{3+}}$ is dominated by the ${}^6{P}_{\text{7/2}}{\to }^8{S}_{\text{7/2}}$ transition between the first excited state and the ground state of ${\mathrm{Gd}}^{\text{3+}}$ detected at around 318 nm. Time-resolved CL of the ${}^6{P}_{\text{7/2}}$ level monitoring the ${}^6{P}_{\text{7/2}}{\to }^8{S}_{\text{7/2}}$ transition shows a temperature-dependent lifetime which decreases from 0.76 ms at 12 K to 0.69 ms at 300 K, in contrast to an increasing intensity of the ${}^6{P}_{\text{7/2}}{\to }^8{S}_{\text{7/2}}$ transition by a factor of more than 3.5 in the same temperature range. The decay is of the Inokuti–Hirayama-type indicating energy transfer between ${\mathrm{Gd}}^{\text{3+}}$ ions. Due to the overall weak splitting of the ${}^6{P}_{\text{7/2}}$ and ${}^8{S}_{\text{7/2}}$ multiplets phonon replica with energies of 100 and $\text{588\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ can be assigned.