Eu-Doped AlGaN/GaN Superlattice-Based Diode Structure for Red Lighting: Excitation Mechanisms and Active Sites

Abstract

In this work, we have established the effects of postgrowth annealing and Eu implantation, followed by annealing on an AlGaN/GaN superlattice-based diode structure, containing Mg-doped GaN top p-cap layers. The study is based on the combined information from different optical techniques, such as Raman, photoluminescence, and photoluminescence excitation. We have shown that the diode structure exhibits a stable crystalline quality even after annealing under high temperature and high pressure (HTHP) conditions (1400°C in 1 GPa N 2 ). Furthermore, we have demonstrated that the implanted Eu ions reached the first quantum wells of the diode structure and that the postimplantation thermal annealing partly removed the implantation defects, recovering some of the as-grown luminescence and optically activating the Eu 3+ in the diode structure. An in-depth study of the Eu 3+ population mechanisms was realized through room temperature photoluminescence excitation. A model was built based on the different excitation bands originated from the materials present in the diode structure, demonstrating that an energy transfer between the AlGaN/GaN superlattice excitons and the Eu 3+ ions occurs, therefore enlarging the excitation pathways for the ion's red luminescence. In addition, Eu 3+ luminescence was observed not only with above but also with below GaN bandgap excitation. The temperature dependent study of the 5 D J → 7 F J transitions allowed to tentatively provide the Eu 3+ intraionic assignments of the diode structure. We have demonstrated that at least three nonequivalent active sites are created by the Eu implantation in the diode structure: Eu1, Eu2, and Eu−Mg defect in both configurations Eu0 and Eu1(Mg).

Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation

“…Indeed, this absorption is enhanced with the increase of the fluence, confirming an increase in the density of irradiation-induced defects (i.e., a higher number of states in the bandgap obtained for the highest fluence), accompanied by a redshift of E CPPB as seen from the absorption below the ZnO bandgap. This enhanced absorption below the bandgap due to irradiation or implantation-induced defects has already been reported in other wide-bandgap semiconductors such as III-nitrides [46,47].…”

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

“…The 5 D0 → 7 F0 transition is characterized by its singlet character, i.e. no crystal field splitting is allowed for 5 D0 and 7 F0 levels, implying that the number of the observed 5 D0 → 7 F0 transitions corresponds to the number of non-equivalent active sites if accidental overlaps are not considered [32,44,81,83,84]. Fig.…”

“…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].…”

“…As an alternative to in situ RE incorporation, ex-situ ion implantation constitutes a suitable method to obtain a controlled doping profile with concentration even beyond solubility limits [18,25,26,32,[42][43][44][45][46][47]. This technique requires post-implantation thermal annealing to recover the implantation-induced damage and to optically activate the RE ions.…”

Efficient One-Pot Synthesis of Bright Blue-Emitting Ce3+-Based Phosphor: Application for the Construction of Warm White-Light-Emitting Diodes and Anticounterfeiting

“…13,14 Ln-based green and red phosphors have been extensively investigated because of their characteristics of easily sensitized luminescence. 15,16 However, it is hard to achieve Ln-based phosphors with blue emission, which remains a challenging task. 17 To fabricate WLEDs, green-emitting and red-emitting Ln-based phosphors are usually codoped with other blue phosphors such as organic fluorophores, silicon nanoparticles, and quantum dots, 18,19 which might require different excitation wavelengths, limiting their potential applications in the light industry.…”