Terahertz photoconductivity of Pb1-xSnxTeIn

We have analyzed photoconductivity in Pb1−xSnxTe(In) under the action of ∼100 ns long terahertz laser pulses with the wavelength varying from 90 to 280 μm in the temperature range 4.2–300 K. Strong photoresponse has been observed at all laser wavelengths used. Two types of photoresponse have been detected. Positive persistent photoconductivity, which is observed at T<10 K is due to photoexcitation of impurity states, whereas negative nonpersistent photoresponse prevailing at higher temperatures T∼25 K results from free carrier heating. Specific features of photoconductivity mechanisms are discussed.