Self-Organized Eu-Doped GaN Nanocolumn Light-Emitting Diode Grown by RF-Molecular-Beam Epitaxy

Abstract

High-concentration doping of Eu ions working as luminescent centers in GaN is required to improve light output of optical devices. GaN nanocolumns can be used to achieve high crystallinity in high-concentration Eudoped GaN (GaN:Eu). In this study, optical properties of a GaN:Eu nanocolumn grown by RF-plasma-assisted molecular-beam epitaxy (RF-MBE) are investigated and GaN:Eu nanocolumn light-emitting diodes (LEDs) are demonstrated. Suppression of yellow luminescence and concentration quenching of PL intensity are observed at RT for GaN:Eu nanocolumns. When the effect of Eu concentration on optical properties is analyzed using rate equation, an increase in the Eu concentration is observed to affect 5 D 0 lifetime corresponding to back transfer, and not the effective cross-section corresponding to transfer efficiency. Based on these results, GaN:Eu nanocolumn LEDs are fabricated on an n-type (111) Si substrate. Clear rectification characteristics and sharp red luminescence are observed. The light output increases with increasing Eu concentration up to a concentration of 6 Â 10 20 cm À3 . These results suggested that GaN:Eu nanocolumns provide feasible crystal to realize novel optical devices.

Synthesis and Applications of III–V Nanowires

“…Eu-doped GaN was studied to be used as an active layer for planar red LEDs . Recently, Sukegawa et al realized Eu-doped GaN NWs by MBE and inserted it into n-type and p-type GaN sections for an LED structure . EL emission at 620 nm was observed.…”

“…495 Recently, Sukegawa et al realized Eudoped GaN NWs by MBE and inserted it into n-type and ptype GaN sections for an LED structure. 496 EL emission at 620 nm was observed. Because the Eu doping level is much higher in the GaN NWs than the planar film before luminescence starts to quench, this could be a good option for GaN NWs to realize efficient red LEDs for microLED displays.…”

Eu3+ optical activation engineering in Al Ga1-N nanowires for red solid-state nano-emitters

“…The incorporation of the rare-earth (RE) trivalent europium ions (Eu 3+ ) into III-N layers [16][17][18][19][20][21][22][23] and nanostructures [24][25][26][27][28][29][30][31][32] was proved as an excellent strategy to obtain red emission characterized by the sharp and stable Eu 3+ intra-4f 6 transitions. This approach was successfully implemented for in situ Eu 3+ -doped GaN-based emitting devices [31,[33][34][35][36][37][38], with Eu 3+ -related luminescence external quantum efficiency (EQE) values reaching ~29% at room temperature (RT) and ~48% at 77 K [39]. In order to sustain the EQE value up to RT, it is important to overcome the RE thermal quenching.…”

Recent progress in red light-emitting diodes by III-nitride materials

“…Takagi et al demonstrated a drastic Eu luminescence enhancement of 20-fold via Mg co-doping [196]. The same group also reported that the Mg co-doped GaN:Eu nanocolumns using red LEDs had feasible crystal quality even though there was heavy Eu doping at up to 6 × 10 20 cm -3 [200]. [207].…”