the PL intensity of defect level at low temperatures ( about 10 K) is even much higher than the transition of the band to band transitions. what is the main mechanism of the PL intensity with varying temperatures?
Chuang Li
There are many possible reasons for which PL intensity might change (decrease) with temperature:
- Thermal broadening of PL intensity peak inducing a decrease of PL intensity, is the first possible mechanism,
- Electron-Phonon and photon-phonon interactions may have also an influence and both lead to a decrease of PL intensity ,
- But in your case, it seems that defects states are playing the dominant role. It is a highly probable thermally induced population redistribution over different states of the same defect which can have energy separation higher than the energy bandgap. Some of these states might be separated from other states of the same defect by thermal energy barriers confining the electrons at low T on the fundamental state of the defect which is optically active (because of selection rules) hence the intense low temperature PL spectrum. At higher temperatures, electrons can thermally escape from this fundamental defect level and go populate some other states of the same defect which are optically inactive because of selection rules (hence the observed decrease and even disappearence of PL response).
Best regards,
Professor A. Kadri
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