In AZO and ZnO thin films, two peaks centered at around 371-381 and 387 to 391 nm. From the literature range between 371-381 nm peaks assigned to UV (band to band transitions or NBE emissions) and range between 387 to 391 nm peak assigned to one of the shallow donor levels (which could not be excited to
the conduction band because some excited electrons lose energy through phonon emission).
Can anyone explain what are the possible shallow donor levels for this emission.
PL spectra normally show an excitonic peak in the UV region and a defect-related peak in the Vis region.
The excitonic peak in ZnO film shows a blue shift with Al doping.
In visible region, the pure ZnO film exhibits a broad peak centred around ∼500-510 nm related to the defects which is suppressed for the AZO films.
Al doping in ZnO can also enable red shifts in the defect-related PL peak. (peak shifting ~520-540 nm).
The possible defects in ZnO are zinc interstitials and oxygen vacancies. These defects are maily responsible for n-type conductivity in undoped ZnO film. Also, other defects such as O interstitials, vacancies of Zn, O sitting at Zn site, can also possible.
May be you can deconvoluted your PL data to see these effect.
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