Temperature dependence of near ultraviolet photoluminescence in ZnO/(Mg, Zn)O multiple quantum wells

Abstract

We report on temperature dependence of excitonic photoluminescence ͑PL͒ from ZnO/͑Mg, Zn͒O multiple quantum wells ͑MQWs͒. Two kinds of MQWs having different barrier heights grown by laser molecular-beam epitaxy showed significantly different temperature dependences of PL spectra; in ZnO/Mg 0.27 Zn 0.73 O MQWs, the PL peak energy at 50-200 K was a monotonically increasing function of temperature, which was opposite to that ascribed by band gap shrinkage. Moreover, spectra taken at 95-200 K encompassed two peaks, both of which originated from recombination of localized excitons. The temperature-induced shift ͑redshift-blueshift-peak duplication-redshift͒ at 5-300 K is caused by a change in the exciton dynamics with increasing temperature due to inhomogeneity and the exciton localization effect. On the other hand, the corresponding dependence in ZnO/Mg 0.12 Zn 0.88 O MQWs ͑lower barrier height͒ was similar to that in bulk II-VI semiconductors.

Response to “Comment on ‘Room temperature photoluminescence from ZnO quantum wells grown on (0001) sapphire using buffer assisted pulsed laser deposition’” [Appl. Phys. Lett. 101, 256101 (2012)]

“…The band gap values obtained from the photoluminescence measurements showed Stokes shift compared to the values obtained from absorption spectra which could be attributed to the carrier localization associated to the potential fluctuations in ZnO QWs. 4,5 Furthermore, we do not agree with Gu's Comment 1 that the ZnO QWs in our arctile 2 do not have good crystalline quality and sharp interfaces, and the blueshift shown in Figs. 1 and 2 of Ref.…”

“…Phys. Lett In response to a Comment 1 by X. Q. Gu on our paper, 2 we would like to clarify that the calculation of the band edge of ZnO quantum wells (QWs) with different well layer thicknesses in the range of 4 to 1 nm discussed in our paper 2 is based on solving the time independent Schr€ odinger equation using finite square potential well approximation [3][4][5] not the infinite square potential well. However, in the published manuscript, 2 it was inadvertently mentioned as infinite square well approximation.…”

Quantum confinement effect on Gd2O3 clusters

“…Already some results have been obtained for ZnO by Makino et al 7 But insulators with even stronger ionicities are still uninvestigated. In a previous paper, 8 we presented the first observation of the gap blueshift of Gd 2 O 3 :Eu 3+ nanoparticles obtained by a sol-lyophilization process.…”

Optical properties of ZnO-based quantum structures

“…Our spectral assignment are based on (1) the well width dependence of Stokes shift (difference between the energies of absorption and luminescence bands), (2) the temperature dependence of PL spectra, and (3) the spectral distribution (luminescence energy dependence) of decay time constants of luminescence [27,35,31,36,37,38]. Here, the temperature dependence of the PL spectrum in a QW in the case of magnesium composition of 0.27 is described in detail.…”

“…The features of excitonic spontaneous emission in the well layers are sensitively affected by the dynamics of recombination of localized exciton states, which significantly vary with temperature. Readers should refer to the original articles for details [35].…”