Investigation of Cadmium Telluride Grown by Molecular-Beam Epitaxy using Micro-Raman Spectroscopy Below and Above the Laser Damage Threshold
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The effects of visible laser light on cadmium telluride (CdTe), grown by molecular beam epitaxy, are studied at low (48 µW/µm2) laser power densities using micro-Raman spectroscopy. The Raman spectrum of CdTe shows no notable change at lower power density ~48 µW/µm2 for prolonged laser exposure. At higher power density ~480 µW/µm2, the Raman spectrum is significantly changed and strong Te-related peaks appear in the spectrum, even for short laser exposure times suggesting that photo-induced Te enrichment happens at the CdTe surface at high laser power density. The temperature rise is estimated from observed shifts in the Te and CdTe optical phonon peaks and modeled using finite-element simulations. At laser power 480 µW/µm2, the CdTe exhibits a rise of ~44 ºC above room temperature while the observed change in Te temperature is significantly higher, ~179 ºC. The approach illustrates steps needed to establish the laser damage threshold for CdTe.