PbTe(Ga)–New Multispectralir Photodetector

Abstract

Doping of the lead telluride - narrow-gap semiconductor - with gallium results under certain conditions in the Fermi level pinning in the gap thus providing the semiinsulating state of material. Besides that, the persistent photoconductivity effect is observed at a temperatures T < T, = 80 K. The photoresponse kinetics consists of two parts: the slow one with the characteristic time t_char, going up to 10⁴ s at T = 4.2 K, and the fast part with t_char of the order of 10 ms. We have measured the spectra of a fast part of the photoresponse using the Fouriertransform spectrometer “Bruker” IFS- 113v. The photoconductivity is observed in two spectral regions: in the middle- and far - infrared. Response in the middle-infrared consists of the ordinary fundamental band and a strong superimposed resonance-like structure just at the bandgap energy. The position of this spectral line may be tuned in a wide range (3.5-5.5) Pim by variation of temperature and/or composition of a lead telluride-based alloy. This middle-infrared photoresponse becomes considerable already at T = 160 K. The photoresponse in the far-infrared may be depending on the excitation conditions an analogous resonance-like structure at a wavelength 70 fum, or a broad band with the cutoff wavelength at least higher than 500 fum, which is the highest cutoff wavelength for the photon detectors observed up to date.