Alexander E. Klimov

Injection currents in narrow-gap (Pb1−xSnxTe):In insulators

The low-temperature current-voltage characteristics of narrow-gap (Pb1−xSnxTe):In have been studied experimentally and calculated for a wide range of electric fields. It is shown that the obtained data are satisfactorily described in terms of a space-charge-limited current model in the presence of traps. The concentration and energy depth of the traps have been estimated.

Photosensitivity of Pb1−x SnxTe:In films in the terahertz region of the spectrum

An increase in the electrical conductivity is observed in the Pb1−xSnxTe:In/BaF2 films subjected to laser radiation with a wavelength λ=336.8 μm (the frequency of ∼0.9×1012 Hz) at the liquid-helium temperature; this increase cannot be accounted for by a heating of the sample. The observed photosignal-relaxation time does not exceed the RC time constant of the measurement circuit (this time constant amounts to fractions of seconds) and is much shorter than in the case of illumination within the fundamental absorption band of Pb1 − xSnxTe:In. The results obtained relate to an increase in the low-frequency permittivity ɛ as a result of excitation (by photons of the submillimeter region) of one or two transverse optical phonons in the center vicinity of the Brillouin zone at the branch responsible for the ferroelectric phase transition. This circumstance brings about an increase in the space-charge-limited injection current that flows from the contacts without a generation of free charge carriers in the bulk.

Giant Magnetoresistance in Narrow-Gap Ferroelectric-Semiconductor PbSnTe:In

A giant (up to 10 4 ) magnetoresistance effect in magnetic fields B ≈ 4 T was observed in MBE-grown PbSnTe:In films under conditions with space-charge-controlled limitation of injection currents. The relative change in the electric current depended on the strength and mutual orientation of the two (electric and magnetic) fields. The effect is discussed in terms of a model in which the static dielectric permittivity ϵ of the material is assumed to be dependent on crystallographic orientation. Experimental data that show how the permittivity ϵ of PbSnTe:In films and their current-voltage characteristics depend on the orientation of the electric field vector at B = 0 are reported.

Photosensitivity of Pb1 − xSnxTe:In films in the region of intrinsic absorption

The steady-state photocurrent in the fundamental absorption region of Pb1 − xSnx Te:In films is calculated with the field injection of electrons from the contact and their capture by traps in the bulk taken into account. The calculated and experimental current-voltage characteristics are compared at liquid-helium temperature. The represented experimental data on the dependence of the Hall effect on the injection level agree well with the considered model.

Industrial prospects of Pb1 − xSnxTe:In with x > 0.3 solid solutions for photodetectors with extended sensitivity spectral range

Photoelectric properties of Pb1 − xSnxTe:In films with composition x > 0.3 in the temperature range from 4.2 to 80 K have been investigated. High sample sensitivity to black-body radiation has been discovered at the temperature of helium, and as the temperature of the radiation source decreases the sensitivity increases, which can be connected with the optical-frequency transition in the short-wavelength infrared and terahertz spectral range. The detectivity value D* = 8.2 × 1016 cm · Hz1/2/W corresponding to the NEP = 3.1 × 10−18 W/Hz1/2, has been obtained at detector temperature 4.2 K and TBBR = 15 K.

Terahertz detectors based on Pb1−xSnxTe:In films

Results of experimental studies of Pb1−xSnxTe:In films grown by molecular beam epitaxy with the tin concentration close to band inversion are presented. An optimal concentration of indium is determined, and films with x > 0.3 are obtained, where the so-called metal-insulator transition is observed. Photoconductor prototypes are fabricated, and the photocurrent induced by free electron laser radiation in the range of 140–205 µm is measured. A possibility of using photoconductors for recording the own radiation of a body heated to a temperature of 300 K in a passive mode, including systems of image registration in the terahertz spectral range, is estimated.

Photocapacitance effect in narrow bandgap PbSnTe (In)

Low frequency permittivity of PbSnTe(In) solid solution was investigated in darkness and under illumination. ε=2,000-300,000 was found depending on temperature and illumination. For the first time the increase of ε under illumination by about two orders was observed at LH temperature. Far IR cut off of the effect was estimated. It was found that the best correlation of calculations with experimental data took place if we supposed the presence of narrow band of PbSnTe In sensitivity within 300-400 μm spectral region.

Specific temperature-related features of photoconductivity relaxation in PbSnTe:In films under interband excitation

The time dependences of variations in the photoconductivity of PbSnTe:In films in the range of T ≈ 19—25 K upon interband excitation are studied. It is found that the character of conductivity relaxation after switch-off of illumination depends on the duration and intensity of the preceding illumination. In this case, the characteristic times of relaxation for various modes of illumination can differ by more than an order of magnitude. The obtained results are discussed in the context of a model assuming the presence of a quasicontinuous spectrum of capture levels in the band gap of PbSnTe:In and also a possible effect on the parameters of these levels of the ferroelectric phase transition, the temperature of which is found to be in the temperature range under study

Thin-film PbSnTe:In/BaF2/CaF2/Si structures for monolithic matrix photodetectors operating in the far infrared range

We report for the first time on the creation of 288 × 2 matrix photodetectors with an element size of 25 × 25 μm based on PbSnTe:In/BaF2/CaF2/Si structures and present their threshold characteristics. The detection ability of about 90% elements ranges from 7.2 × 1012 to 8.7 × 1012 cm Hz0.5/W at T = 21.2 K. The proposed technology opens ways to the creation of monolithic matrix photodetectors operating in the far-IR range.

Submillimeter matrix photosensitive device on PbSnTe : In films

Principles of operation of large-scale photodetector arrays for image visualization in a submillimeter spectral range are considered. Parameters of a thermal picture produced on an intermediate screen by a submillimeter component of radiation of an object with a temperature of about 300 K are estimated. Photodetector array parameters required for registration of the intermediate screen radiation are analyzed. The possibility of creating large-scale photodetector arrays on PbSnTe : In films for imaging objects with a room temperature without additional submillimeter illumination is shown.