This experimental research is focused on the nature and properties of hydrogen-containing deep level impurities in semiconductors. Hydrogen is often used for passivation, for example to fill dangling bond states in amorphous silicon, reducing the density of states in the energy gap. In other cases, under study here, hydrogen may attach to a deep level impurity resulting in a new complex which is electrically active. Examples of such deep level states in n-type silicon are AuH, AuH2 and FeAuH centers, whose identities and structures may be established by IR absorption and Deep Level Transient Spectroscopy (DLTS). The work carried out under this grant uses the methods cited and also ESR, on impurity doped semiconductor specimens which are typically hydrogen annealed and electron irradiated using a Van de Graaff accelerator. Of interest are the electrical properties and the structural properties of such defects. The work is also concerned with theoretical modeling of the defects and their properties. This research program is interdisciplinary in nature and typically involves one or more undergraduate and graduate students, who receive excellent training in preparation for careers in industry, government laboratories or academia. %%% This experimental research is focused on the nature and electrical properties of a specific type of impurity in semiconductors such as silicon. Silicon is a basic material in producing microelectronic devices for computers and many other applications. Silicon must be highly purified for successful use in producing transistors and other microelectronic devices. Even extremelly small concentrations of impurities, such as gold or iron, or of defects such as vacant lattice sites, can be very important. It is useful to know the details of the defects that can occur, and to learn of the possible electrical actions that can result. This project is devoted to learning the electrical and structural properties of a class of impurity defects in silicon and related semiconductors. These defects are produced by a combination of a "deep level" impurity such as gold or iron, with hydrogen. Hydrogen is sometimes introduced in semiconductor processing because in many cases it "passivates", or reduces the electrical effects, of certain impurities or defects. However, in the cases under study in this work, the hydrogen has the opposite effect, of making the normally passive "deep impurity" electrically active. The methods involved in this research involve semiconductor specimens which are intentionally doped with, eg, iron or gold, and subsequently annealed in hydrogen and bombarded with high energy electrons from a Van de Graaff accelerator. These steps make the defects; study is done by a combination of optical absorption in the infrared range, electron spin resonance, and a technique for measuring electrically active defect properties known as "Deep Level Transient Spectroscopy". This basic research adds to scientific understanding of silicon and other semiconductors, which are at the heart of the microelectronics and computer technologies. The information may be useful in the design and successful operation of manufacturing processes for microelectronics. This research program is interdisciplinary in nature and typically involves one or more undergraduate and graduate students, who receive excellent training in preparation for careers in industry, government laboratories or academia. ***
