Spectra and energy levels of Gd3+(4f(7)) in AlN

We report crystal-field splitting investigations of Gd3+(4f(7)) energy levels determined from high resolution energy (Stark) level cathodoluminescence (CL) spectroscopy of Gd-implanted 2H-aluminum nitride (AlN) in the wavelength range 250 to 320 nm and at temperatures 12, 77, and 300 K. The CL spectra are interpreted in terms of lattice-sum and crystal-field splitting models that assume implanted Gd replaces Al substitutionally in cationic sites in AlN having C-3v point group symmetry. The CL spectra are associated with Gd3+ ions in a single site. A rms deviation of 7 cm-1 was obtained between 43 observed and calculated Stark levels. The intense UV emission at 318 nm (the P-6(7/2)-->S-8(7/2) transition) can be understood in terms of multiplet-to-multiplet branching ratios.