Solid-state electronics is based on devices constructed from sequentially deposited layers of semiconductors, metals and insulators. This paper discusses some of the performance limiting parameters of such structures with particular attention being given to their surface and interfacial properties.
This paper reviews the rationale for the use of heterojunctions in devices. Through the use of specific examples, the physical properties of this powerful technique are demonstrated. Comparisons of common epitaxial growth techniques suitable for heterojunction growths are given.
Progress in thin-film optical coatings during approximately the past decade is reviewed. Steady improvements in all areas and spectacular advances in some have been made. The art of design has been revolutionized by the enormous growth in computers. Exciting applications including mirror coatings for the x-ray region are emerging. Our understanding of the fundamental characteristics of films, microstructure, and its influence on other properties such as stress, adhesion, and moisture adsorption has improved greatly. There are indications that the standard deposition technique of thermal evaporation in vacuo is not always able to achieve the ultimate in demanded performance, and proposed modifications are discussed.
Stratified optical materials and coatings play an important role in improving the efficiency of solar conversion processes. At present the best-known stratified media are multilayer and graded-index films. Stratified media are used as heat mirrors, selective absorbers, antireflective films, and transparent insulation. Graded-index films can be homogenous materials, spatially oriented structures, or etched materials. Such films and materials improve efficiency and allow for innovation in energy-efficient windows, passive and active energy conversion, and photovoltaics. The horizons of invention can be expanded by considering new materials, techniques, and concepts that can increase the efficiency of energy utilization in buildings and transform solar energy into heat, light and electrical power. The stability requirements for materials to effectively collect and transmit solar energy are extremely demanding. This, coMbined with the need for inexpensive production methods, creates a broad area for innovative scientific research. We describe several approaches and materials systems for two broad application categories: 1) low-conductance, high-transmittance systems and 2) solar absorbers.
Reducing or eliminating reflectance of electromagnetic radiation from surfaces has important technical and commercial applications. Graded-index surfaces are of interest because they have low reflectivity over much broader spectral regions and angles of incidence than conventional thin film coatings. This paper reviews methods to calculate the reflectivity and to estimate the refractive-index profile of graded-index surfaces. Charactertistic properties and techniques to produce graded-index surfaces are reviewed. The results of recent measurements of laser-induced damage to graded-index surfaces are summarized.
This paper reviews the deposition methode of single element metallic films, refractory films, silicides, vacuum epitaxy of metallic films, silicon and GaAs. The vacuum deposition techniques are: rf sputtering, magnetron sputtering, e-beam deposition, vacuum epitaxy and molecular beam epitaxy. Finally, the application of these films to microwave devices and integrated circuits is reviewed.
Options for coating III-V semiconducting material with insulating layers are discussed with regard to the physical and electrical properties of the deposited layers. Emphasis is on those techniques which minimize charging effects in the interfacial layers. Results on gallium arsenide, indium phosphide, indium arsenide, indium antimonide and indium gallium arsenide are discussed.
A review of materials technologies for the growth of multilayer device structures is given. It is concluded that new device structures employing ultrathin layers and abrupt interfaces will be grown by metalorganic chemical vapor deposition (MOCVD) or by molecular beam epitaxy (MBE).
This review covers the two key aspects of ion implantation: 1. damage production in a crystalline Si substrate and eventual amorphization of damaged region of the substrate and, 2. the recrystallization of the damaged layers. The latter has been divided into two separate topics; recrystallization behavior of damage in bare-implantated Si substrates and in through-oxide implanted Si substrates. Pictorial examples (TEM micrographs) of recrystallization behavior of various types of damage structure on furnace, laser and rapid thermal annealing are given in the text. The effect of secondary defects on redistribution of impurities has been illustrated. The electrical properties of the implanted region has been explained by considering damage-impurity interactions.
Important parameters for evaluating and characterizing thin films include (1) film thickness and index of refraction, (2) volume absorption coefficient of the film material, (3) surface absorption, (4) impurities and structure of the deposited film, (5) surface irregularities and defects, (6) light scattering, (7) adherence, hardness, and resistance to chemical attack, and (8) thickness nonuniformity and the resulting apparent change in optical figure. These parameters and some of the many ways to measure them will be discussed. To avoid systematic errors, it is advisable to use two or more independent techniques whenever possible.
A review of the science and technology of chemical sensing using planar micro-fabricated thin film potentiometric electrodes is presented. Those aspects of technology of stratified media that are especially peculiar to this class of structures, namely fabrication of thin film composites consisting of inoraanics, organics, gels and heterogeneous mixtures of these on planar electronic substrates are discussed. Problems encountered in patterning of this broad range of materials for the fabrication of chemical sensor arrays are emphasized.