The work deals with studies of the grain size and surface state effect on photoelectric and transport properties of
PbTe(In) films in the temperature range from 4.2 K up to 200 K under irradiation of a blackbody source and terahertz
laser pulses. The PbTe(In) films were deposited on insulating substrates kept at the temperatures TS equal to -120 (see manuscript)
250C. AFM, SEM, Auger spectroscopy and X-ray diffraction were used to study the film microstructure. Increase of the
TS value led to mean grain size growth from 60 up to 300 nm. All films had a column-like structure with the columns
nearly perpendicular to the substrate plane. It is shown that microstructure of the films strongly affects the
photoconductivity character in the terahertz region of the spectrum. Positive persistent photoresponse is observed at low
temperatures in the polycrystalline films. For these films transport and photoelectric properties are determined by the
grain volume and impurity state specifics. Nanocrystalline films have all features of non-homogeneous systems with
band modulation. For these films only negative photoconductivity is observed in the whole temperature range. Possible
mechanisms of the photoresponse formation are discussed.
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.
Zero-bias spin separation generated by homogeneous optical excitation with terahertz radiation in quantum wells
is reviewed. In gyrotropic semiconductor structures spin-dependent asymmetry of electron scattering induces
a pure spin current which results in a spin separation. We consider the relaxation mechanism yielding the
spin current due to the energy relaxation of a heated electron gas and the excitation mechanism caused by the
scattering assisted free carrier absorption. An experimental access to these phenomena provides the application
of an external magnetic field converting the spin current into a measurable net electric current. We discuss
microscopic and phenomenological theory of these effects, give an overview of experimental data, and address
several applications.
The photogalvanic effects, which require a system lacking inversion symmetry, become possible in SiGe based quantum well (QW) structures due to their built-in asymmetry. We report on the removal of spin degeneracy in the k-space of SiGe nanostructures. This is concluded from the observations of the circular photogalvanic effect induced by infrared radiation in asymmetric p-type QWs. We discuss possible mechanisms that give rise to spin-splitting of the electronic subband states.
Microwave absorption in GaAs and influence of hot charge carriers
on formation and dissociation prcxeses of xund states was studied.
I'1k investigated classical cyclotron resonance in pure GaAs epitaxial layers. This made it ible with tt lp of contact I method to
determins a norecjilibrium electron mobility . Smooth decreasir of exciton
1umirscence with inoreasir of microwave power was observed and a model
describir this ptnomenon was suggested.
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