Cadmium telluride thin-film detectors of nuclear radiation

Semiconductor detectors for X-ray and γ radiation are developed based on thin cadmium telluride (p-n-CdTe) films possessing a columnar structure. The detector structures are formed on molybdenum substrates by CdTe sublimation and magnetron sputtering of cadmium. The p-CdTe films have a thickness of d=30–150 μm and a resistivity of ρ≥10³–10⁷ Ω cm. The single crystal grains in the films have an average size of 50–100 μm and are oriented perpendicularly with respect to the Mo substrate. In comparison to the usual single crystal CdTe detectors, the proposed thin-film single crystal CdTe detectors possess a more perfect structure, since the grain boundaries act as effective sinks for defects. The energy resolution of the new generation of CdTe detectors reaches ∼5 keV for the 59.6 keV line of ²⁴¹Am at room temperature.     

Variation of the reflection coefficient of semiconductors in a wavelength range from 0.2 to 20 μm under the action of ultrasonic waves

The effect of ultrasonic waves on the spectral coefficient of radiation reflection from the surface of semiconductors used in solar energy converters is considered. A change in the reflectance of semiconductors before and after ultrasonic treatment is determined. It is shown that acoustic stimulation of the semiconductor surface and subsurface layers determines the radiation reflection conditions.     

Effect of ultrasound on the adhesion of metal coating to nonferrous metals

The effect of ultrasound on the adhesion of metal coating to nonferrous metals has been studied. It is established that the ultrasonic treatment of metal coatings increases their adhesion strength. This effect is explained by the fact that the momentum imparted by ultrasound to atoms of the coating is sufficient to cause their migration over a certain distance from the surface into depth of the nonferrous metal substrate.     

Acoustostimulated expansion of the short-wavelength sensitivity range of AlGaAs/GaAs Solar cells

The effect of ultrasonic waves on the spectral sensitivity of solar energy converters based on AlGaAs/GaAs heterostructures has been studied. Ultrasonic treatment of a zinc-doped graded-gap Al_xGa_1−x As film leads to the formation of a surface layer sensitive to electromagnetic radiation in the wavelength range λ < 0.551 μm. It is established that this layer is formed as a result of the acoustostimulated inward diffusion of zinc from the surface to the bulk of the graded-gap layer. The observed expansion of the short-wavelength sensitivity range and an increase in the efficiency of nonequilibrium charge carrier collection in AlGaAs/GaAs solar cells are due to improvement of the crystal defect structure and the dopant redistribution under the action of ultrasound.     

Acoustostimulated change in the optical absorption coefficient of gallium arsenide in the 0.81–1.77 μm wavelength range

The effect of ultrasonic waves on the spectral absorption coefficient of gallium arsenide (GaAs) in the 0.81–1.77 μm wavelength range. The treatment of GaAs single crystals with ultrasonic waves leads to a change in their coefficients of absorption of electromagnetic radiation. This phenomenon is related to the fact that an acoustic wave, being an energy carrier, modified a defect system of the crystal and produces a redistribution of impurities in the crystal lattice. The interaction of photons with acoustogenerated defects changes the optical absorption coefficient near the edge of the fundamental absorption band of GaAs.     

Alternating-strain-induced drift of nonequilibrium charge carriers in GaAs photodetectors

The drift of nonequilibrium charge carriers in GaAs was studied. It is demonstrated that the electric and acoustic (ultrasonic) fields significantly influence the transport of charge carriers in photodetectors based on piezoelectric semiconductors with traps.     

Acoustostimulated changes in the density of surface states and their energy spectrum in <Emphasis Type="Italic">p</Emphasis>-type silicon single crystals

The effect of ultrasonic treatment at various powers on the density N _SS of surface states and their energy spectrum in p-type silicon single crystals has been studied. It is established that, depending on the regime of ultrasonic treatment, N _SS can either increase or decrease compared to that in the initial single crystals. This is accompanied by a redistribution of the total charge of the surface states over the silicon bandgap width. This phenomenon is related to the fact that an acoustic wave, being an energy carrier, modifies a defect subsystem of the crystal by redistributing the impurity atoms and by generating new defects.