Identification of intrinsic deep level defects responsible for electret behavior in T1GaSe(2) layered semiconductor

Unusual behavior of pyroelectric current signal polarity near the Curie point ( T-c) was observed for TIGaSe2 a ferroelectric-semiconductor. It has been revealed that the polarity of the spontaneous polarization near T-c depends on the sample poling prehistory. In particular, applying an external electric field only in the temperature range of the paraelectric state during cooling regime in darkness brought to the depolarization current at I with the sign opposite to the external field polarity. Otherwise, if the sample was poled in the temperature interval of the incommensurate phase, pyroelectric current exhibits a peak at T-c with the polarity that is the same as for the external poling electric field. These observations indicate that internal electric field is present in the bulk and near-surface layer regions of the electrically poled single crystal TIGaSe2. Possible mechanisms and origins responsible for the internal electric fields in TIGaSe2 are discussed. It is shown that the formation of internal electric fields in TIGaSe2 is due to charging of intrinsic native defects during the poling process.