Semiconductor Multilayer Structures Research Articles

Aging and degradation of transparent copper iodide thin film electrodes for functional electronic devices

Transparent CuJ copper iodide thin-film electrodes are widely used in various optoelectronic devices, such as solar cells, electroluminescent displays, touch screens, multifunctional photoconverters, etc. Their advantages are high transparency, because CuJ absorbs light in a limited range of wavelengths, which allows them to transmit visible light, making them ideal for transparent devices, low cost, because copper iodide is an inexpensive material, making it economically viable for mass production, simplicity fabrication, as CuJ can be easily deposited on various substrates using simple film deposition techniques such as vacuum deposition and magnetron sputtering. However, transparent CuJ type thin-film electrodes are subject to aging and degradation, which can reduce their performance and service life. The main factors affecting the aging and degradation of CuJ are the processes of oxidation, diffusion, degradation under the influence of light, and humidity. Despite numerous studies in the direction of obtaining high-quality thin films of copper iodide, today there is a need for a detailed study of the processes of their aging and degradation of properties. Therefore, in this article, we investigated the degradation processes of transparent upper copper iodide electrodes of thin-film multicomponent semiconductor heterostructures. This article shows the features of the use of film copper iodide in multilayer thin-film semiconductor structures. The influence of atmospheric conditions and lighting on the values of the rates of degradation of electrical resistance of copper iodide in semiconductor thin-film structures was studied. It has been found that atmospheric exposure to oxygen, moisture and other factors increases the electrical resistance of the copper iodide top electrode, and the use of Elastosil sealant does not lead to appreciable improvement. Heterostructures in vacuum are minimally affected by external factors, and therefore a significant increase in their CuJ upper electrode resistance values indicates the predominant role of aging of copper iodide films, which is not related to atmospheric conditions. It was established that natural sunlight significantly increases the degradation of copper iodide films, which should be taken into account when forming and using the corresponding thin film structures.

Semiclassical theory of electronic states in multilayer semiconductors. Part 1

States of electrons in multilayer semiconductor structures are theoretically investigated in the semiclassical approximation, where one-electron wave functions of the stationary Schrödinger equation are calculated in the presence of various types of potential, which is a slowly varying function of the coordinate. It is determined that the energy spectrum of electrons in the potential in the quadratic approximation takes discrete values and the steepness of the energy spectrum depends on the parameters of the expansion of the potential in coordinates.

Effects of intermetallic compound layer thickness on the mechanical properties of silicon-copper interface

Intermetallic compounds (IMC) are found in the dual-layer composite, such as Si/Cu composite in multilayer semiconductor structures, and are often ignored in simulations that aim to predict the mechanical properties. The interface model of Si/Cu composites with different thickness of IMC layer is first established by molecular dynamics simulation. Then this study analyzed the elastoplastic behavior and adhesion behavior of the Si/Cu interface and the effect of IMC on the fracture properties. The simulation results demonstrate that the Si/Cu interface fails in a quasi-brittle fracture mode. The crack propagates along the interface between Si and the IMC layer. An apparent dislocation emission and large plastic deformation are found exclusively in the Cu layer. The thickness of the IMC layer increased from 2 to 10 Å, and the critical strain energy release rate increased from 14.48 J/m2 to 19.76 J/m2, while the equivalent modulus is not increase monotonically. Therefore, the IMC is of high significance for predicting the mechanical properties of the dual-layer composite.

Growth and characterization of II-VI semiconductor multilayer quantum-well structures for two-color quantum well infrared photodetector applications

The design, growth, and characterizations of ZnCdSe/ZnCdMgSe semiconductor multilayer quantum-well structures for two-color quantum-well infrared photodetectors (QWIPs) are reported. The energy band and quantum well states are computed in a ZnCdSe/ZnCdMgSe single quantum well for both infrared detection regions. The sample has been grown in a multichamber molecular beam epitaxy system. The good crystalline quality of sample and its lattice matching to the InP substrate are investigated by high-resolution x-ray diffraction and transmission electron microscopy analysis. These structural measurements also confirm the good agreement between the design and the grown structure. The band-to-band and interband transition energies are experimentally determined by photoluminescence and contactless electroreflectance, respectively. The intersubband absorption spectra are investigated by Fourier transform infrared spectroscopy at room temperature. This multilayer structure represents a significant technological validation of the capabilities and potential of InP-based II-VI materials for engineering two-color QWIP devices. This paper provides a detailed methodology for the growth and in-depth characterization of such a complex high precision multilayered structure.

Protected Long-Distance Guiding of Hypersound Underneath a Nanocorrugated Surface.

In nanoscale communications, high-frequency surface acoustic waves are becoming effective data carriers and encoders. On-chip communications require acoustic wave propagation along nanocorrugated surfaces which strongly scatter traditional Rayleigh waves. Here, we propose the delivery of information using subsurface acoustic waves with hypersound frequencies of ∼20 GHz, which is a nanoscale analogue of subsurface sound waves in the ocean. A bunch of subsurface hypersound modes are generated by pulsed optical excitation in a multilayer semiconductor structure with a metallic nanograting on top. The guided hypersound modes propagate coherently beneath the nanograting, retaining the surface imprinted information, at a distance of more than 50 μm which essentially exceeds the propagation length of Rayleigh waves. The concept is suitable for interfacing single photon emitters, such as buried quantum dots, carrying coherent spin excitations in magnonic devices and encoding the signals for optical communications at the nanoscale.

Особенности электродвижущих сил в многослойных полупроводниковых структурах

Особенности электродвижущих сил в многослойных полупроводниковых структурах

Stresses modeling in multilayer semiconductor structures of automobile regulators and predicting the reliability of their operation

The problems of increasing the reliability of microelectromechanical systems are considered on the example of an automobile voltage regulator. A model of the process is proposed and a study of the effect of temperature on the formation of stress fields in semiconductor structures of active elements of the controller is carried out. The studies assumed of a possible reason for the change in the parameters of the regulator due to the appearance of defects in the crystal structure of the semiconductor material in the structures of integrated voltage regulators. For the study, a mathematical model was proposed that describes the behavior of a semiconductor element of a real car voltage regulator. It was found that the distribution of stresses in the structures is uneven and the maximum value of stresses reaches the edges., An increase in temperature gradients in the structures of regulators leads to the formation of dislocations that change the electrical characteristics of devices. As a result of modeling, it has been established that thermoelastic stresses arising in the process of manufacturing and functioning of semiconductor structures of a regulator in regulators of this type can cause a change in the structure of a semiconductor device due to relaxation of elastic stresses at dislocations. in cars. Measures are proposed, including thermostating of the sensitive elements of microelectromechanical structures, which will increase their service life.

Subbarrier and Overbarrier Electron Transfer through Multilayer Semiconductor Structures

The transparency coefficients of a semiconductor structure consisting of alternating asymmetric potential barriers and wells, where the Bastard condition is taken into account, are calculated. It is shown that in the structure, an oscillation of the transmission coefficient of electrons depending on their energy is observed, which is caused by the interference of the de Broglie waves coming to the barrier and reflected from the potential barrier. The electronic states of a multilayer semiconductor structure consisting of alternating potential wells and barriers are analyzed.

Measurement of thermal transport properties of selected superlattice and thin films using frequency-domain photothermal infrared radiometry

Thermal transport properties in multi-layered semiconductor samples are reported using modulated photothermal infrared radiometry (PTR). The cross-plane thermal conductivity and diffusivity of thin AlxGa(1-x)As layers and AlAs/GaAs superlattices were determined by fitting solutions of the heat equation for multi-layered systems to PTR data. The thermal conductivity of an AlxGa(1-x)As film with x = 0.5 was found to be lower than an AlxGa(1-x)As film with x = 0.33 which is expected as scattering from alloy disorder is maximized for x = 0.5. In addition, it was found that thermal conductivities of AlAs/GaAs superlattices decrease when the superlattice period is decreased for a constant total thickness which is expected since the number of AlAs/GaAs interfaces (which impede thermal transport) increases as the period decreases. The maximum PTR amplitude signal was found to occur when the diffusion length of the thermal wave is on other order of the thickness of the semiconductor layer. The accuracy and applicability of photothermal infrared radiometry to the study of semiconductor multilayer structures are further discussed in the paper.

On Modeling the Distributions of Minority Charge Carriers Generated by a Wide Electronic Beam in Planar Multilayer Semiconductor Structures

The paper presents the results of modeling the distributions of minority charge carriers generated by a wide electron beam in two-layer semiconductor structures. The analytical results obtained using the matrix method are compared with the results of calculations obtained using the numerical method of finite differences. The studies are carried out for epitaxial structures of “solid solution of cadmium-mercury telluride –cadmium telluride” and two-layer gallium arsenide.

Possibility of Applying the Matrix Method to Modeling the Cathodoluminscescence Caused by a Wide Electron Beam in a Planar Multilayer Semiconductor Structure

Results are presented from investigating the possibility of applying the analytical matrix method to modeling the diffusion of nonequilibrium minority charge carriers and the subsequent cathodoluminescence caused by a wide electron beam in a planar structure of semiconductor optoelectronics with any number of layers. The proposed technique allows calculations to be made with an accuracy sufficient for practical use in electron probe technologies.

Подбарьерный и надбарьерный перенос электронов через многослойные полупроводниковые структуры

Подбарьерный и надбарьерный перенос электронов через многослойные полупроводниковые структуры

Comparison of analytical and numerical modeling of distributions of nonequilibrium minority charge carriers generated by a wide beam of medium-energy electrons in a two-layer semiconductor structure

An analytical matrix method that makes it possible to calculate the distributions of nonequilibrium minority charge carriers generated in multilayer planar semiconductor structures by external influence is described. For the case of generation of nonequilibrium minority charge carriers by a wide electron beam in a two-layer structure, the results of model calculations using the analytical matrix method with the results of calculations using a numerical conservative difference scheme are compared. It is shown that the method allows to carry out calculations of the distributions of nonequilibrium minority charge carriers in a relatively short time with an accuracy sufficient for practical use in electron probe technologies.

Sub-barrier and Above-barrier Electron Transport Through Multilayer Semiconductors

The transparency coefficients of the semiconductor structure consisting of alternating asymmetric potential barriers and wells are calculated, where taken into account the Bastard condition. It is shown that both in the above-barrier and over barrier passage of electrons, tunneling oscillations arise. The amplitude, in this case, is determined not only by the values of the wave vectors, but from the values of the effective masses of the current carriers. This oscillation does not disappear even in symmetric structures if they have a difference in the effective masses of current carriers located in two neighboring regions. In symmetrical structures, an oscillation of the coefficient of the above-barrier passage of a particle depending on its energy should be observed without taking into account the Bastard condition. Calculations show that for equal values of the width of the well and the potential barrier, as well as jumps in the potential of the barrier or well, the amplitude of the oscillations of the coefficient of over-barrier passage of particles is greater than the coefficient of passage above the well. In the case of an asymmetric structure, these considerations remain valed, but the physical nature of the parameters, for example, the number of oscillations, reflection and transmission coefficients, strongly depends on the ratio of the effective masses of electrons in neighboring layers and from the ratio of the height of the left and right potential barrier (regarding to the well). In an asymmetric (and in a symmetric, but with different effective masses of electrons in different layers) semiconductor structure, oscillation should be observed depending on the coefficient of transmission through the potential barrier on the energy of electron. This oscillation is caused by the interference of waves going to the barrier and reflected from the potential barrier. Such an interference phenomenon in the structure does not disappear even in a symmetric structure due to the difference in the effective masses of electrons located in different regions of the structure. The electronic states of a multilayer semiconductor structure consisting of alternating potential wells and barriers are analyzed.

Numerical Tool for Analyzing Planar Semiconductor Multilayers Within the Two-Fluid Hydrodynamic Model Framework

We present a numerical tool to study the electromagnetic response of planar semiconductor multilayer structures when nonlocal effects of the materials are considered, where a two-fluid hydrodynamic model is adopted. The electric field is expanded in terms of scalar wave functions, whose governing equations and corresponding boundary conditions are derived. It is found that scattering matrices are well suited to handle the nonlocal response within the hydrodynamic framework, indicating that the proposed method can readily be extended to deal with the nonlocal effects when more than two types of charge carriers are included. We found that the spatial dispersion would lead to a higher transmission for a hyperlens while they may make the lens disfunctional.

Control of local stress in semiconductor silicon structures

Residual stress distribution in multilayer semiconductor structure is complicated and has a significant impact on device characteristics and yield, therefore their study is one of the actual tasks of modern device engineering. Purpose of the present work was to develop methods of estimation of actual residual stress distribution at the whole area of semiconductor structure and its elements as well.The estimation of residual stress distribution at the area of semiconductor structure was carried out on the basis of determining of local deformation of some areas of the structure by Makyoh topography. This method is based on consequent measurements of intensity of Makyoh image elements of the structure along the chosen direction followed by calculation of micro-geometrical profile and curvature radius.The estimation of residual stress of topological elements Si–SiO system was carried out by means of calculation of interference pictures obtained in a film-substrate gap after separating of film edge from substrate along open window perimeter.Analytical expressions relating semiconductor structure image characteristics with their deformation were developed by means of finite elements method. The expressions allow determining of local residual stress of chosen area of the structure. The examples of stress calculations in real structures are given.Proposed residual stress calculation methods allow to take into consideration character and curvature form of substrate, and also to estimate their magnitude in real topological elements of semiconductor circuits.

Heat transfer through soldered and bonded joints of multilayer semiconductor devices studied by laser photothermal beam-deflection method

Thermal wave propagation through solid-solid non-ideal interfaces in multilayer semiconductor devices is considered. A theoretical model is developed for thermal wave propagation, and the laser photothermal probe beam deflection method is used for experimental study of heat transport through multilayered samples with vertical joint interfaces. Experimental and theoretical results are presented for bonded and soldered joints. It is shown that, in general case, both the thermal resistance and the heat capacity of the joint should be considered to describe adequately experimental data and to determine thermophysical properties of a separate layer. It is shown that the real thermal resistance of a soldered joint may be much higher than the predicted one basing on tabulated characteristics. The paper demonstrates that the laser photothermal beam-deflection methods can be applied for testing the thermal contact quality between elements of multilayered semiconductor structures, for example, a multijunction solar cell, assembling by various technologies. These methods make possible to evaluate quantitatively the thermal resistance and heat capacity of thermal contacts at the micrometer scale.

INFRARED DETECTORS BASED ON TERNARY SEMICONDUCTOR QUANTUM STRUCTURES

The development of growth process of multilayer semiconductor structures enables investigation of a new class of infrared detectors – detectors on quantum structures. The current trends of infrared receivers’ development are caused by active material research for a variety of nanostructures. The current state of development of infrared quantum structure detectors using ternary semiconductor alloys is considered. The maximal detectivity values of traditional detectors and quantum structure detectors are presented. The analysis of parameters for different types of materials and structures is performed.

Light propagation in tunable exciton-polariton one-dimensional photonic crystals

Simulations of propagation of light beams in specially designed multilayer semiconductor structures (one-dimensional photonic crystals) with embedded quantum wells reveal characteristic optical properties of resonant hyperbolic metamaterials. A strong dependence of the refraction angle and the optical beam spread on the exciton radiative lifetime is revealed. We demonstrate the strong negative refraction of light and the control of the group velocity of light by an external bias through its effect upon the exciton radiative properties.

Omnidirectional reflector using linearly graded refractive index profile of 1D binary and ternary photonic crystal

The effect of the refractive index profile on the omnidirectional reflector (ODR) of one dimensional dielectric and semiconductor multilayer structure having linearly graded material has been simulated using transfer matrix method. The theoretical analysis shows that the proposed structure works as a perfect mirror within a certain wavelength range. These wavelength ranges can be completely controlled by the refractive index profile of a graded semiconductor layer and also observed that these wavelength ranges are also controlled by refractive index parameters. Reflectance characteristics of 1D binary and ternary photonic crystal (PC) structure have been studied. This property shows that the ODR range of structure increased when a third layer of semiconductor added in a binary photonic crystal.