Features of Differential Current-Voltage Characteristics of Tunnel Structures Based on PbTe:In Single Crystals at Low Temperatures

The current-voltage characteristics of metal-insulator-semiconductor tunnel contacts based on bulk lead telluride single crystals doped with indium with an impurity content of 2 at. % were investigated at low temperatures (T < 40 K). The features of the differential conductivity of the contacts and its derivative associated with the indium impurity were analyzed. The hysteresis of the differential conductivity with a change in the sweep direction of a bias voltage is associated with metastable states on impurities at T < 20 K. The features of the current-voltage characteristics associated with the appearance of forced oscillations in the energy of band states in the subcontact region of the semiconductor were discovered. These oscillations appear when the lifetime of nonequilibrium impurity states approaches the period of bias voltage modulation oscillations. A phase analysis was performed, and the temperature dependences of such features of the differential characteristics were studied. The results made it possible to estimate the energy position of the single-electron impurity center-above the Fermi level position by ≈ 35 meV. Independent confirmation of predominantly paired electron filling of impurity states of indium-a impurity center with negative correlation energy has been obtained.