Hello, I have acquired an excitation intensity photoluminescence map of ZnO thin film (380 nm) on a silicon wafer at 16K, that was thermally processed with RTA. The excitation wavelength range was from 300 nm to 500 nm and the emission wavelength range was recorded from 380 nm to 800 nm.
In this map, for a near band edge excitation of 375 nm, there are two very intense PL peaks at about 520 to 530 nm that stand out in the whole map. These peaks are barely excited when the excitation is 300 nm to about 340 nm. Between 340 nm to 375 nm there is a wide dispersed photoluminescent area that culminates in the two peaks when the excitation wavelength reaches 375 nm. My question is why these sub-band gap defects are not excited strongly also when the energy is a lot higher than the band gap of ZnO (i.e at 320 nm for example)? The counts for these two states at 375 nm are in the range of 600 but at 325 nm in the range of 100. many thanks
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