Optical processes of red emission from Eu doped GaN

Abstract

A single crystalline Eu-doped GaN was grown by gas-source molecular beam epitaxy and photoluminescence (PL) properties were studied. The PL spectra show red-emission at 622 nm originating from intra 4f-4f transition of Eu 3C ion without band-edge emission of GaN. The peak shift of the red-emission with the temperature variation from 77 K to room temperature is less than 1.6 meV, and thermal quenching of the luminescence was found to be small compared with the band-to-band transition. Fourier transform infrared spectra showed an absorption peak at about 0.37 eV, which may be due to a deep defect level. The intensity of the red luminescence and the defect-related absorption peak increased with increasing Eu concentration, and a close correlation in the intensity was observed between them. These results suggest that the deep defect level plays an important role in the radiative transition of Eu 3C ion in GaN and the optical process for the luminescence at 622 nm was discussed with the relation to the defect. q

Total photoluminescence spectroscopy of GaN nanocrystals doped by Eu3+ions

“…The absorption band at ~4.42 eV could be associated with other higher excited state in GaN-nc but also it can be related to Eu 3+ charge transfer absorption band (CT) which is very strong in the case of Eu 3+ ions in other bulk hosts [17]. The absorption band centered at ~3.14 eV has been attributed to the absorption through the defect states, since its energy position is significantly below the energy gap of bulk GaN, and since this position is in agreement with the defect related energy levels reported by other authors [18,19]. J. Sawahata et al [18] proposed that in epitaxially grown GaN layer doped by Eu, these deep defect states (~370 meV) introduced by Eu, play a dominant role in the energy transfer process.…”

Lanthanide impurity level location in GaN, AlN, and ZnO

“…Because of the wide band gap, as compared to e.g. InN or GaP, these compounds are optically transparent [1,2], and many studies were performed on the luminescence of lanthanide impurities like Pr 3+ [3,4,5]. Unfortunately, GaN:Ln 3+ is still not applied as thinfilm electroluminescent material because of the low luminescence efficiency at room temperature [6,7].…”

Thermal quenching of luminescence and isovalent trap model for rare‐earth‐ion‐doped AlN

“…The model of the energy-transfer process with formation of a shallow intermediate state was justified on the results of FEL spectroscopy. It has been shown that the formation of trap states is essential for the RE ion-core activation in semiconductors [33,[42][43][44][45][46][47][48].…”