Abstract
A new fine structure of red luminescence (RL) was observed in unintentionally doped ZnO at low temperature. The new RL was demonstrated to be different from the one assigned to Fe3+ center by Heitz et al and visible only under the excitation of light capable of generating excitons. The RL can be extremely enhanced at the incident frequency in resonance with the donor exciton and the intensities of some adjacent lines separated by ∼4 meV are thermally populated with the increase in temperature. The new structured RL was studied in the terms of photoluminescence (PL) and PL excitation spectra and the origin was discussed taking into account the internal transitions of transition metal elements, structure defects, and native point defects. There is a great possibility that the new structured RL arises from the excited states converted from bound excitons, for example, the excitons or the electron and hole pairs bounded by the donor and acceptor pairs (DAPs) of O and Zn vacancies, because the binding energy determined by the equation of DAP fluorescence is highly in accordance with the theoretic values reported in the literature.
Highlights
As a wide-gap semiconductor having optoelectronic applications overlapping with GaN, ZnO has some advantages that the binding energy is relatively large (∼60 meV) and the fairly highquality bulk single crystals are available via relatively simple growth technology, resulting in a potentially lower cost for ZnO-based devices
RL2 is misidentified as RL1 if the sample is not excited resonantly with the donor bound exciton (DX) line or the PL spectra are recorded with an insufficiently-high resolution
In the PL excitation (PLE) spectra taken at the energies where the RL2 lines are visible, such as B and C marked by the arrows in Figure 4(a), two PLE peaks are clearly identified at ∼3.361 and ∼3.408 eV, which are highly in accordance with the DX line determined from the PL spectrum of this sample and the first excited state (DXn=2) estimated using the binding energy of DX.1
Summary
As a wide-gap semiconductor having optoelectronic applications overlapping with GaN, ZnO has some advantages that the binding energy is relatively large (∼60 meV) and the fairly highquality bulk single crystals are available via relatively simple growth technology, resulting in a potentially lower cost for ZnO-based devices. One of the reasons is believed to be in association with the relatively high density of native defects in ZnO, such as oxygen and zinc vacancies (VO and VZn), interstitials (Oi and Zni), and antisites (OZn and ZnO), giving rise to the difficulty of p-type doping. Based on the binding energy determined by the equation of DAP fluorescence, the excitons or electrons and holes trapped on the DAPs of O and Zn vacancies (VO−VZn) were suggested to be responsible for the new structured RL
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
