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The deformation effects in electronic spectra of the ternary layered semiconductors TlGaS 2 , TlGaSe 2 and TlInS 2 are considered. It is shown that the influence of hydrostatic pressure, thermal expansion and variation of composition in solid solutions on the band gap of the crystals investigated can be described in the framework of one common model of deformation potentials. This model appears to be close to that of layered semiconductors of the A 3 B 6 group, attesting to the fact that the main principles of formation of band structure in these two groups of layered crystals are the same.

We report on the characteristics of metal-p-type high resistance TlGaSe2 semiconductor junction barrier fabricated by deposition of indium and gold metals. The electrical properties of /TlGaSe2/ semiconductor contacts were monitored as a function of temperature in the range of ∼80–300 K using current–voltage ( I − V ) and capacitance–voltage ( C − V ) measurements. Device characteristics of I n /TlGaSe2/ A u showed rectification properties. From forward bias I − V characteristics it was revealed that the increase of current is slower than the predictions by Schottky barrier theory. The rectification properties of I n /TlGaSe2/ A u semiconductor device were simulated by the Mott barrier model where the presence of an undoped layer on the semiconductor surface is assumed, and measurements and computational simulation agreed on the validity of this model. C − V measurements showed that at higher temperatures I n /TlGaSe2/ A u barrier showed a capacitance from accumulation toward depletion mode, whereas at low temperatures the barrier capacitance degradation was found. The observed C − V of I n /TlGaSe2/ A u does not significantly change over the entire bias range ± 30 V, confirming that the I n /TlGaSe2/ A u is fully depleted, thus the structures are Mott barrier. First-principles electronic band diagram calculations showed that introduction of S e -atom vacancies in the various sites of TlGaSe2 unit cell greatly affects the electronic band structure of this semiconductor in an increasing manner in band gaps with respect to stoichiometric compound. Consequently, the S e - vacancies localized inside the thin surface layer of TlGaSe2 are responsible for high average surface electrical resistivity of the material and could be proposed as a physical basis for the existence of native insulator layer on TlGaSe2 surface. Thus we propose a model for TlGaSe2 crystal which is comprised from an electrically conducting bulk semiconductor sandwiched between two high resistivity thin surface sheets. We suggest that the selenium vacancy defects on the surface of TlGaSe2 layered semiconductor are also responsible for the memristive behavior of this compound.

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