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Carrier trapping and recombination in TlGaSe2 layered crystals



In nominally undoped layered TlGaSe2 crystals the trapping centers have been investigated by photo-induced current transient spectroscopy (PICTS). Five acceptor and donor traps have been detected. Quite large magnitudes of capture cross-sections for donor traps at 0.23 and 0.45 eV have been determined. The depth-resolved free-carrier absorption (FCA) technique has been applied for the investigation of the majority hole lifetime, τR, at 295 and 77 K. The pronounced τR reduction with increasing injection level is attributed to the trapping effect of the minority electrons which provides a way of estimating trap centers concentration. A moderate τR variation across layer planes is observed but no carrier diffusion related to the recombination on the external crystal surfaces is detected. Moreover, abnormally sharp τR drop is found for carrier concentration above 1017 cm−3. The possibility of excess hole and electron special separation due to compositional stacking faults and the successive their enhanced recombination at high excess carrier concentrations is discussed.

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