Enhancing the photoresponse of a TlGaSe₂ semiconductor for ultraviolet detection applications

Anomalous transformations of conductivity, photoconductivity and photovoltaic response were discovered in TlGaSe₂ crystals after its treatment within an external electric field. To investigate the effect samples were cooled from room temperature down to ∼80 K under the external electric field. After the cooling process the external electric field was discarded. Following this treatment it was found that a built-in internal electric field was induced, which strongly affects the transport properties of TlGaSe₂ crystals. The most important outcome was observation of the rectifying type current–voltage (I–V) characteristics which appeared as a consequence of the built-in electric field. As a result a significant increase in the photovoltaic response was observed predominantly in the ultraviolet (UV) portion of the electromagnetic spectrum. The observed effects are discussed on the basis of the metal–insulator–semiconductor structure having a thin native insulator layer, which reveals itself after the treatment in the external electric field. Thus, a new method for building UV photodetectors based on TlGaSe₂ crystals is introduced. (paper)