<title>Rare earth doped gallium nitride layers for photonics applications</title>

Enhancement of 1.5 μm emission under 980 nm resonant excitation in Er and Yb co-doped GaN epilayers

“…It has been well established that Er and ytterbium (Yb) co-doping in a solid host is an effective approach to enhance the Er emission at 1.5 lm under 980 nm resonant excitation. 24,[27][28][29][30][31] This is due to the fact that the absorption cross section of Yb 3þ at 980 nm is about one order of magnitude larger than that of Er 3þ . In the Er and Yb co-doped materials, Yb 3þ ions act as sensitizers by absorbing 980 nm excitation photons and then transferring energy resonantly from their excited 2 F 5/2 state to the 4 I 11/2 level of Er 3þ ions.…”

“…In the Er and Yb co-doped materials, Yb 3þ ions act as sensitizers by absorbing 980 nm excitation photons and then transferring energy resonantly from their excited 2 F 5/2 state to the 4 I 11/2 level of Er 3þ ions. 24,[27][28][29][30][31] This efficient resonant energy transfer process is facilitated by the close match between the energy levels of the 2 F 5/2 state of Yb 3þ and the 4 I 11/2 state of Er 3þ . This transfer is then followed by a rapid nonradiative decay to the first 4 I 13/2 excited manifold of Er 3þ ions, after which a direct transition to the 4 I 15/2 ground state of Er 3þ occurs, resulting in the 1.5 lm emission.…”

“…31 The incorporation of Yb at a doping level similar to that of Er is thus expected to provide a nearly one order of magnitude enhancement in the effective optical absorption efficiency at 980 nm and hence a higher emission efficiency at 1.5 lm. 31 Different methods have been employed to obtain Er and Yb co-doped semiconductors so far, including magnetron sputtering 27,28 and ion-implantation. 29 Compared to these methods, in-situ co-doping of Er and Yb via epitaxial growth has the advantages of providing a more uniform distribution of RE concentrations and reduced impact to the crystalline quality of the host crystals; 30 however, this had not been previously attempted in GaN.…”

“…The expected major benefit of Yb and Er co-doping is the enhancement of the absorption efficiency at 980 nm via the sensitization effect. 24,[27][28][29][30][31] The room temperature PL spectra of the same set of Er þ Yb:GaN epilayers grown under varying Yb flow rates from 0 to 2.4 SLM and a fixed Er flow rate of 2.2 SLM were measured under 980 nm resonant excitation, and the results are presented in Fig. 4(a).…”

Improved optical and electrical properties of low-temperature sputtered GaN by hydrogenation

“…However, significant O contamination is not uncommon for sputtered GaN. [12][13][14] The PL spectra of the 100 nm films are plotted in Fig. 2͑a͒.…”