Fabrication and optoelectronic properties of Ga₂O₃/Eu epitaxial films on nanoporous GaN distributed Bragg reflectors

Nanoporous GaN distributed Bragg reflectors (DBRs) with a high reflectivity (~ 92%), which was fabricated via a doping selective electrochemical etching process, were used to deposit Eu-doped β-Ga₂O₃ films by using pulsed layer deposition. Structural and chemical composition analyses indicated that the 900 °C-annealed film in air has the best crystalline quality and highest photoluminescence (PL) efficiency. The epitaxial relationship between the β-Ga₂O₃: Eu film and DBR mirror was Ga₂O₃ (\(\overline{2}\)01)║GaN (0001) with Ga₂O₃ [010]║GaN [\(\overline{1}\)2\(\overline{1}\)0]. Compared to the Eu:Ga₂O₃ film on reference template, the 900 °C-annealed film on the DBR mirror presented a ~ 20-fold enhancement in the PL emission. The performance enhancement was attributed to light-coupling enhancement of the buried DBR mirror. Because of the good electrical properties of the annealed films, the fabricated DBR substrates pave the way for developing a range of rare-earth-doped Ga₂O₃ optoelectronic devices.