Red light emission by photoluminescence and electroluminescence from Eu-doped GaN

Abstract

Visible light emission has been obtained at room temperature by photoluminescence ͑PL͒ and electroluminescence ͑EL͒ from Eu-doped GaN thin films. The GaN was grown by molecular beam epitaxy on Si substrates using solid sources ͑for Ga and Eu͒ and a plasma source for N 2. X-ray diffraction shows the GaN:Eu to be a wurtzitic single crystal film. Above GaN band gap photoexcitation with a He-Cd laser at 325 nm resulted in strong red emission. Observed Eu 3ϩ PL transitions consist of a dominant narrow red line at 621 nm and several weaker emission lines were found within the green through red ͑543 to 663 nm͒ range. Below band gap PL by Ar laser pumping at 488 nm also resulted in red emission, but with an order of magnitude lower intensity. EL was obtained through use of transparent indium-tin-oxide contacts to the GaN:Eu film. Intense red emission is observed in EL operation, with a spectrum similar to that seen in PL. The dominant red line observed in PL and EL has been identified as the Eu 3ϩ 4 f shell transition from the 5 D 0 to the 7 F 2 state.

Spectral and time-resolved photoluminescence studies of Eu-doped GaN

“…[1][2][3][4][5][6][7][8][9] In addition, several EL device structures based on GaN:Eu have been demonstrated. [1][2][3][4][5] The optimization of present EL devices, however, requires a more detailed understanding of the incorporation, excitation, and emission properties of Eu 3ϩ ions in the GaN host matrix.Several studies have recently appeared focusing on the preparation and optical properties of GaN:Eu. 4 -11 Based on the comparison to RE ions in other III-V semiconductors ͑e.g., InP:Yb, 12 GaAs:Er 13 ͒, the most probable lattice location for Eu 3ϩ ions in GaN are ͑substitutional͒ Ga sites, which have C 3V symmetry.…”

“…This broad excitation band overlaps higher lying intra-4 f Eu 3ϩ energy levels, providing an efficient pathway for carrier-mediated excitation of Eu 3ϩ ions in The visible and infrared light emissions from rare-earthdoped GaN ͑GaN:RE͒ are of significant current interest for applications in thin-film electroluminescence ͑EL͒ devices. [1][2][3][4] For achieving red light emission, the 5 D 0 → 7 F 2 intra-4 f transition of trivalent Eu 3ϩ ions seems most promising. Intense red photoluminescence ͑PL͒ around 622 nm from GaN:Eu ͑as-grown and ion-implanted͒ has been reported from several research groups.…”

“…[1][2][3][4] For achieving red light emission, the 5 D 0 → 7 F 2 intra-4 f transition of trivalent Eu 3ϩ ions seems most promising. Intense red photoluminescence ͑PL͒ around 622 nm from GaN:Eu ͑as-grown and ion-implanted͒ has been reported from several research groups.…”

“…4 Solid sources were used to supply the Ga ͑7N purity͒ and Eu ͑3N purity͒ fluxes. A rf plasma source was used to generate atomic nitrogen.…”

Photoluminescence properties of in situ Tm-doped AlxGa1−xN

“…[1][2][3] Photoluminescence ͑PL͒ and cathodoluminescence ͑CL͒ data have been reported from nearly all lanthanide ions doped into GaN. [1][2][3] Visible EL devices based on RE-doped GaN, however, have only been demonstrated from GaN:Eu ͑red͒, 1,5,6 GaN:Er ͑green͒, 7 and GaN:Tm ͑blue͒. 8 One of the main challenges in using RE-doped GaN for full-color display applications is obtaining efficient blue emission.…”