Influence of heat treatment on the electrophysical properties of thin films of copper-indium diselenide

An investigation of the structural, electrical, optical, and thermophysical properties is carried out on thin polycrystalline films of the ternary semiconductor CuInSe₂, which is potentially useful for fabricating solar cells. The thin films were obtained by thermal evaporation of CuInSe₂ and Se powder from two independent sources and by high-vacuum deposition in a closed cell (quasiequilibrium deposition). The influence of annealing in air on the parameters of the thin films is analyzed, and the dynamics of variation in the properties of the films are investigated as a function of the annealing time. Temperature dependences of the electrical conductivity, mobility, and thermal conductivity of CuInSe₂ thin films are given together with the spectral dependence of the short-circuit photocurrent of a photosensitive Au-CuInSe₂-Au structure. Zh. Tekh. Fiz. 67, 34–38 (March 1997)     

Change in the electrophysical properties of water by microwave radiation

A study is made of the change in the electrophysical properties of water subjected to low-power superhigh-frequency radiation. Experimental values of high-frequency conductivity and ion current are obtained for water irradiated within the ranges of 3.8 and 10–12 GHz. Spectra of the optical density of water in the ultraviolet region are also presented. An analysis is made of the connection between these spectra and the observed changes in the high-frequency properties of water. Siberian Physico-Technical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 20–26, April, 1997.     

Structural and electrophysical characteristics of YBCO films on sapphire

We present experimental results for the structural and electrophysical characteristics of YBCO films deposited on sapphire substrates without an interface layer. The films were deposited by laser sputtering of a target. We establish certain relationships between the structural and electrophysical characteristics of the films. We show the films’ electrophysical parameters are determined by the number of "defective" blocks whose [010] axes are at random angles relative to the [100] axis of the substrate. V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zaved, Fizika, No. 5, pp. 75–78, May, 1998.     

Electrical activity of radiation-induced defects in indium antimonide and arsenide surface-barrier structures

The electrical activity of defects induced by high-energy proton irradiation inInSb andInAs semiconductors is investigated by etching from their surfaces a layer whose thickness is equal to the depth of defect localization and preparing a MOS structure. Two layers of defects of different origin and electrical are detected, and their influence on the surface-state energy spectrum, the recombination activity, and the kinetic characteristics of the defective layer is revealed. The threshold increase in the photosensitivity and the speed of performance and vanishing of the burst noise in MOS structures are found. The results obtained are explained for a model of conservation of the local electrical neutrality that specifies the position of the Fermi energy levels in irradiated semiconductors. Tomsk State University of Control Systems and Radioelectronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 37–45, September, 1999.     

Effects of low-temperature diffusion on the electrophysical properties of Cu-Cr polycor structures

A study has been made of the effects of heat treatment on the specific-resistance distribution in Cu-Cr-polycor structures at 100–400°C. The effects on the specific resistance are explained in terms of low-temperature diffusion of Cr interacting with minor components at the Cu-Cr boundary. Under certain conditions, there is a reduction in the specific resistance at the Cu-Cr boundary, which reduces the longitudinal attenuation in microstrip lines in the uhf range.     

Transition processes occurring under continuous and stepwise heating of GaAs surface-barrier structures

Evolution of the capacitance-voltage (C-U) and current-voltage (I _f-U and I _r-U) characteristics of solid metal-semiconductor structures (Ni/GaAs) in the process of their continuous and stepwise heating are studied. Properties of the initial structures obey the theory of thermionic emission. It has been shown that as a result of continuous heating, the rectifying structures become ohmic at a temperature of T _Ohm=720 K, which is substantially lower than the melting points of the metal or the metal-semiconductor eutectic. For comparison, properties of the structures annealed at different temperatures T _ann are measured after cooling to room temperature (stepwise heating). In this case, I-U characteristics are closer to the initial ones for annealing temperatures T _ann<T ₀=553 K; for T _ann>T ₀, the characteristics display excess currents; and, finally, for T _ann exceeding T ₀ by 200–300 K, the characteristics become purely ohmic. It is suggested that these effects are due to a chemical interaction between Ni and GaAs, which changes the properties of the semiconductor surface.     

Influence of thermopolar processing on the electrophysical properties of anodic tantalum oxide

We have studied the physical mechanisms which lead to failure of Ta-Ta₂O₅-Al thin film capacitors during prolonged exposure to an electric field and elevated temperature. Using a thermally stimulated depolarization technique we have determined the energy spectrum of the point defect levels in the band gap of the oxide in the original structure and in that subjected to fields at high temperature. The changes observed demonstrate an increase in the shallow trap and donor concentration at the interface between the oxide and the external electrode. The transition layer which develops reduces the barrier at the Al-Ta₂O₅ interface, leading to increased injection and, as a result, to increased conductivity. It is shown that the stability of the structure depends on the deposition technique used for the metallic layers: an electrothermal technique yields a more stable structure than a magnetron.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 120–125, September, 1991.     

Frequency and spatial characteristics of the electrophysical parameters of a living tree trunk

The method of vertical electrical sounding is applied to derive the spatial characteristic of the dc resistivity ρ of a living pine trunk, ρ = L-0.85, and the frequency characteristic of the ac resistance R of the same pine trunk, R = f-0.053. The results are simulated by the methods of fractal geometry, according to which ρ = L ^{−h + 2} and $ R \sim f^{ - \tfrac{3} {h} + 1} $ R \sim f^{ - \tfrac{3} {h} + 1} , where h is the walk dimension of the electric current in the trunk. From comparison between the experimental and theoretical results, it follows that h = 2.85 and fractal dimension D = 1/h = 0.35. Since D = 1, conducting layers form a Cantor set.     

Photoelectric and electrophysical characteristics of In2S3-SiOx-Si Structures

Results are presented of the investigation of the effect of two oxidation methods of silicon (chemical and anodic) on the electrophysical properties of In₂1S₃-SiO_x-Si structures. It is shown that the change in the potential barrier height in silicon and the properties of the interface depend on the oxidation method. In the development of solar energy photoconverters, preference should be given to structures on n-type silicon with chemical oxide.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–6, July, 1985.     

Investigation of the electrophysical properties and structures of impurity-defective complexes in silicon doped with palladium

Electric and structural methods are used to investigate formation of impurity-defective complexes in silicon doped with palladium. It is demonstrated that acceptor levels E _C – 0.18 and E _v + 0.34 eV detected in silicon during incorporation of palladium are caused by singly and doubly negatively charged states of [Pd–V] complexes, and the donor level E _v + 0.32 eV is a product of chemical compound of palladium with hydrogen forming the [Pd–H] complex. It is assumed that the palladium impurity in the doped silicon samples causes the elastic crystal energy to change and impurity clouds to be formed around microdefects. An increase in the temperature of palladium diffusion in silicon causes the impurity clouds to decay and the microdefect core sizes to decrease with their subsequent chaining into a needle.     

Peculiarities of the electrophysical characteristics of platinum silicide-silicon contacts under impulsive overloads

The extremal operating states of the active elements of integrated circuits and discrete devices as well as the different actions on semiconductor devices with a Schottky barrier based on metal silicide-silicon contacts lead to a change in their physical parameters. In this work the effect of impulsive overloads on a formed platinum silicide-silicon contact is studied. It is shown, with the help of analytical expressions for the currents in the superbarrier region and in the region of resonant tunneling charge transfer, that under impulsive action a change occurs in both the transitional layer and in the region of space charge; the change is associated with the increase in the concentration of deep levels in the region of space charge that participate in the resonance tunneling. Estimates of the Joule heating by the current flowing in the structures employed do not exceed 100°C, indicating that defect formation under the impulsive actions is nonthermal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 70–73, September, 1988.     

Ultrafast photodetectors based on the interaction of microwave radiation and a photoexcited plasma in semiconductors

The interaction of microwave radiation with the plasma in photoionized semiconductor photocells (CdS, CdSe) placed in waveguide measurement systems is investigated theoretically and experimentally. The interaction of the characteristic waveguide modes with a photoexcited semiconductor plasma is investigated. The dependence of the reflection coefficient and phase of the microwave radiation on the intensity of the optical radiation to be measured is obtained, and the influence of the surface of the semiconductor photocells on these parameters is investigated. A microwave photodetector design based on a millimeter-wave interferometer is developed. Zh. Tekh. Fiz. 68, 94–98 (November 1998)     

Influence of ion implantation on the thermal diffusivity of semiconductors

The influence of ion implantation on the thermal diffusivities of semiconductors are studied using the mirage effect. The dependences of the thermal diffusivities on the implantation doses are obtained. For silicon wafers implanted by boron, phosphorus and arsenic ions, with constant implantation energy, the thermal diffusivities decrease with increasing dose, when the doses are less than some critical values. The theoretical calculation results by using a one-dimensional multilayer model are in good agreement with the experimental ones. On the other hand, for gallium-arsenide wafers implanted with silicon ions, it is found experimentally that the thermal diffusivity increases with the implantation dose.     

BEEM imaging and spectroscopy of buried structures in semiconductors

Ballistic Electron Emission Microscopy (BEEM) has been shown to be a powerful tool for nanometer-scale characterization of the spatial and electronic properties of semiconductor structures. In this article, we will discuss general aspects of BEEM experiment and theory in true ballistic and quasi-ballistic hot carrier transport. We will review the current state and recent progress in the use of the BEEM imaging and spectroscopy to study metal-semiconductor and metal-insulator-semiconductor interfaces, buried semiconductor heterojunctions and novel quantum objects. Various theoretical BEEM models are discussed, and their ability to describe BEEM experiments is examined. Special attention is drawn to the role of the electron scattering in the metal base layer, at the metal–semiconductor interface and in the semiconductor heterostructure on BEEM spectra.     

Electronic structures of impurities and point defects in semiconductors

A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor-and acceptor-like impurities and point defects, which offers a unified understanding for "shallow" and "deep"impurities and point defects. The underlying physics of computational results using different density-functional theorybased approaches are discussed and interpreted in the framework of the bound exciton model.