Resonant indirect excitation of Gd3+ in AlN thin films

Abstract

Optoelectronic and structural characteristics of Er-doped amorphous AlN films J. Appl. Phys. 98, 093514 (2005); 10.1063/1.2127120Effect of growth temperature on morphology, structure and luminescence of Eu-doped GaN thin filmsWe studied the efficient indirect excitation of Gd 3þ ions in AlN thin films. C-axis oriented polycrystalline thin films of Al 0.997 Gd 0.003 N/AlN were grown on fused silica substrates using a reactive radio-frequency magnetron sputtering technique. The intra-orbital electron transition in Gd 3þ showed a narrow luminescence line at 3.9 eV. The photoluminescence (PL) excitation (PLE) spectrum exhibited a peak originating from efficient indirect energy transfer from the band edge of AlN to Gd 3þ ions. The PLE peak shifted and the PL intensity showed a dramatic change when the AlN band gap was varied by changing the temperature. Energy scanning performed by changing the band-gap energy of AlN with temperature revealed several resonant channels of energy transfer into the higher excited states of Gd 3þ . V C 2014 AIP Publishing LLC. [http://dx.

Thermal annealing effects on ultra-violet luminescence properties of Gd doped AlN

“…The thermal expansion coefficient of AlN, fused silica, and sapphire are 4.4 Â 10 À6 , $6 Â 10 À7 , and 7.0 Â 10 À6 K À1 , respectively. 21 The thermal expansion coefficient of AlN is approximately one order larger than that of fused silica. Conversely, when AlN is grown on a c-plane sapphire substrate with almost the same thermal expansion coefficient, the film is epitaxially grown and its band gap becomes close to the bulk value.…”

“…The intra-4f electron transition in rare-earth ions is atomically sharp, and the temperature drift of the emission wavelength is negligible because of the occupied outer orbitals. As a host material for rare-earth elements with emission over a wide wavelength range, wide-band gap nitride semiconductors such as AlN, GaN, and Al x Ga 1Àx N have been explored [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] for developing electroluminescence devices 10,22-24 and electron-excitation devices. 25,26 In particular, for UV rareearth phosphors, lightly Gd-doped AlN or Al x Ga 1Àx N is known to emit an atomically sharp line at approximately 3.9 eV (318 nm).…”

“…25,26 In particular, for UV rareearth phosphors, lightly Gd-doped AlN or Al x Ga 1Àx N is known to emit an atomically sharp line at approximately 3.9 eV (318 nm). [13][14][15][16][17][18][19][20][21][24][25][26] We have reported the emission properties of lightly Gd-doped AlN (Al 1Àx Gd x N) polycrystalline thin films fabricated by using a reactive sputtering technique [19][20][21]25,26 and developed a bright UV emitter pumped by an electron beam. 25,26 The maximum output power we achieved was greater than 1.0 mW/cm 2 .…”

“…26 The intense UV emission is realized by efficient indirect excitation in which the energy absorbed in AlN is transferred to the higher excited states of Gd 3þ , which then relax to the lowest excited state 6 P 7/2 and generates the sharp luminescence by the transition to the ground state 8 S 7/2 . [13][14][15][16][17][18][19][20][21] In contrast to direct excitation of lightly doped rare-earth ions, indirect excitation is rather efficient because the host semiconductor acts as an effective energy absorber with a large optical-excitation cross section. Recently, we found several resonant energy-transfer channels for indirect excitation in thermally annealed Gd-doped AlN films.…”

“…Recently, we found several resonant energy-transfer channels for indirect excitation in thermally annealed Gd-doped AlN films. 21 Post-thermal annealing has drastically improved the UV luminescence efficiency. In this work, we systematically studied thermal annealing effects on the atomically sharp UV luminescence at 3.9 eV (318 nm) of Gd 3þ ions doped in AlN.…”