Superbright photoluminescence of Er3+ ions in pseudoamorphous GaN thin films

High-intensity Er³⁺ photoluminescence at wavelength λ=1510–1535 nm and with a quantum yield of up to 10% was revealed under nitrogen laser pumping (λ=327 nm) in pseudoamorphous GaN films codoped by Er and oxygen. Because Er³⁺ ions do not have a resonant absorption level at this wavelength, the erbium ions are excited only via inter-and intraband recombination energy transfer. A distinctive feature of the Er³⁺ spectrum is its broadening caused by an appreciable contribution of “hot” transitions from the Stark components of the ⁴ I _13/2 multiplet. At liquid-nitrogen temperature, this contribution is dominant. At 77 K, an instability of the spectrum in the form of optical noise was observed in the 1550-to 1570-nm region. Temperature quenching of the photoluminescence was virtually absent. The high Er³⁺ photoluminescence intensity was achieved through proper choice of the multistage (cumulative) anneal regime.