D. E. Dolzhenko

Far infrared high-performance lead telluride-based photodetectors for space-born applications

Abstract A new class of far-infrared photodetectors based on lead-tin tellurides doped with group III impurities is presented. The persistent photoconductivity effect appearing in these materials provides an internal signal integration resulting in a considerable increase in signal-to-noise ratio. The techniques of the photomemory quenching are discussed. In some quenching regimes the effect of giant quantum efficiency stimulation has been observed. The possibility of the generation of photoinduced spatially non-equilibrium states provides the physical evidence for the construction of an integrating “continuous” focal-plane array based on Pb 1− x Sn x Te(In).

Photoconductivity of lead telluride-based doped alloys in the submillimeter wavelength range

Persistent photoconductivity in a Pb0.75Sn0.25Te(In) alloy initiated by monochromatic submillimeter-range radiation at wavelengths of 176 and 241 µm was observed at helium temperatures. This photoconductivity is shown to be associated with optical excitation of metastable impurity states.

Photoconductive response of PbSnTe(In) in the terahertz spectral range

We have analyzed photoconductivity in PbSnTe(In) under the action of ~100 ns long terahertz laser pulses with the wavelength 90 - 500 μm in the temperature range 4.2-300 K. Strong photoresponse has been observed at all wavelengths used. Positive persistent photoconductivity is observed at T < 10 K, whereas negative non-persistent photoresponse prevails at higher temperatures T ~ 25 K. Specific features of photoconductivity are discussed.

Instability of DX-like impurity centers in PbTe : Ga at annealing

The kinetics of variation in the resistance of PbTe:Ga single crystals, with their Fermi level pinned within the band gap, during annealing at temperatures of up to 400°C was studied for the first time. It is shown that annealing the crystals for only several minutes at 200–250°C leads to the transformation of the material, which is semi-insulating at low temperatures, into a strongly degenerate semiconductor with a free electron concentration of about 10−18 cm−3. In other words, annealing results in the decomposition of DX-like impurity centers, which account for Fermi level pinning within the PbTe:Ga band gap. The corresponding activation energy is determined. It is found that high-temperature annealing at about 400°C promotes the tendency to a partial recovery of semi-insulating properties.

Sensitive semiconductor detectors of terahertz radiation for spaceborne applications based on Pb 1-x Sn x Te(In)

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb0.75Sn0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb1-xSnxTe(In)covers all the submillimeter wavelength range.

New type of sensitive infrared and submillimeter radiation photodetectors

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb0.75Sn0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb1-xSnxTe(In)covers all the submillimeter wavelength range.

Sensitive detectors of terahertz radiation based on Pb1-xSnxTe(In)

Indium doped lead telluride-based photodetectors have demonstrated extremely high performance in the terahertz range. These materials reveal a number of advantageous features: “internal” accumulation of the incident radiation, high spatial and temporal stability, high radiation hardness and others

New class of highly sensitive terahertz detectors

The properties of doped semiconductors based on lead telluride, which can be used to design highly sensitive terahertz photodetectors, are described. It is shown that these properties allow one to develop photodetectors with much better parameters than those of the best world analogs.

Submillimeter Radiation ‐ Induced Persistent Photoconductivity in Pb1−xSnxTe(In)

Persistent photoconductivity in a Pb0.75Sn0.25Te(In) alloy initiated by monochromatic submillimeter‐range radiation at wavelengths of 176 and 241 μm was observed at helium temperatures. This photoconductivity is shown to be associated with optical excitation of metastable impurity states.

Submillimeter Radiation–Induced Persistent Photoconductivity in Pb1-xSnxTe(In)

Persistent photoconductivity in a Pb0.75Sn0.25Te(In) alloy initiated by monochromatic submillimeter-range radiation at wavelengths of 176 and 241 μm was observed at helium temperatures. This photoconductivity is shown to be associated with optical excitation of metastable impurity states.