Nanoscale determinant to brighten up GaN:Eu red light-emitting diode: Local potential of Eu-defect complexes

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

“…Theoretical studies revealed that these complexes have a stable configuration [90]. Additionally, it was demonstrated that electrical excitation of GaN:Eu devices favors the excitation of the Eu2 center (also labeled as OMVPE7) [35,91]. In fact, ion implantation might induce a high concentration of cation and nitrogen vacancies (VIII and VN), leading to the incorporation of Eu 3+ ions in cation sites and to the formation of complexes with the generated point defects, which can provide energetic levels within the host's bandgap able to assist Eu 3+ excitation.…”

“…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.…”

GaN:Eu,O-Based Resonant-Cavity Light Emitting Diodes with Conductive AlInN/GaN Distributed Bragg Reflectors

“…The enhancement of the EL peak intensity is obtained by simply dividing the EL peak intensity of the RCLED with that of the normal LED. The EL peak of the normal LED is located at ∼621 nm due to nature of Eu luminescence, 39 while the EL peak of the RCLED shifts toward longer wavelength (∼625 nm), as observed in Figure 2a, due to the effect of the microcavity. A maximum enhancement of 10.9 is obtained at the wavelength of 627.2 nm.…”

“…In contrast, the normal LED exhibits a broader EL spectrum due to the multiple peaks originating from different Eu incorporation sites. 39 The change in spectral properties indicates that luminescence from the RCLED is mainly determined by the cavity Q-factor, rather than the inhomogeneously broadened luminescence of GaN:Eu,O, and a higher cavity Q-factor can result in a narrower line width.…”

Charge state of vacancy defects in Eu-doped GaN

“…[36][37][38] In this technique, a rectangular wave (duty cycle 0.5) from a signal generator (GW Instek, Co., Ltd., AFG-2005) was used to pulse-drive a GaN:Eu LED with a fixed pulse voltage of 6.0 V. The emission from the LED was detected using a spectrometer (Princeton Instruments, Acton SP2500) with a CCD (Charge-Coupled Device, Princeton Instruments, PIXIS 100), with a fixed integration time of 20s. The samples were cooled using a closed-cycle cryostat with vacuum feedthroughs for the electrical connections.…”