Excitation power dynamics of photoluminescence in InGaNGaN quantum wells with enhanced carrier localization
Journal
Journal of Applied Physics
Journal Volume
97
Journal Issue
1
Date Issued
2005
Author(s)
Kazlauskas, K.
Tamulaitis, G.
Mickevi?ius, J.
Kuok?tis, E.
?ukauskas, A.
Cheng, Y.-C.
Wang, H.-C.
Huang, C.-F.
Abstract
Excitation-power dynamics of near-band-edge photoluminescence (PL) peak position in InxGa1−xN∕GaN multiple quantum wells (x∼0.15) was analyzed as a function of well width. The analysis was based on energy reference provided by photoreflectance (PR) spectra. The difference in spectral position of the PR feature and low-excitation PL band (the Stokes Shift) revealed carrier localization energy, which exhibited a remarkable sensitivity to the well width, increasing from 75meV in 2nm wells to about 250meV in 4nm wells. Meanwhile collating of the PR data with the flat-band model for the optical transition energy in quantum wells rendered a relatively weak (0.5MV∕cm) built-in piezoelectric field. The blueshift of the PL peak position with increasing photoexcitation power density was shown to be in qualitative agreement with the model of filling of the band-tail states with some contribution from screening of built-in field in the thickest (4nm) wells. Increased incident photon energy resulted in an additional blueshift of the PL peak, which was explained by a nonthermalized distribution of localized carriers and/or carrier localization in the interface region. Our results are consistent with a concept of emission from partially relaxed large In-rich regions with internal band potential fluctuations, which are enhanced with increasing the growth time.
SDGs
Type
journal article