DX Centers


Book Description

During the last 25 years, the behavior of donors in III-V alloys has been the subject of a very extensive research effort. The research emphasis on AlGaAs compounds is motivated by the industrial importance of AlGaAs/GaAs heterojunction based devices. As seeing it now, "the DX center problem", the behavior of donors in III-V alloys, has shown to be unexpectedly difficult to understand. To determine the microscopic nature of the DX center is still a challenging problem.










Physics of DX Centers in GaAs Alloys


Book Description

The DX center is a defect present in Gallium Arsenide and related alloys when these materials are doped with n-type impurities. The interest for the DX center is twofold: fundamental and technological. For physicists, the DX center exhibits peculiar properties which clearly indicate that it belongs to a new class of defect which had not yet been encountered. The identification of the DX center is also interesting for the technologists now that heterostructures based on the GaAs-GaAlAs system are increasingly used to realize high performance devices. As any deep level, the DX center traps free electrons, thus reducing the free carrier concentration provided by the donor impurities and their mobility.




DX Centers in III-V Semiconductors Under Hydrostatic Pressure. [GaAs


Book Description

DX centers are deep level defects found in some III-V semiconductors. They have persistent photoconductivity and large difference between thermal and optical ionization energies. Hydrostatic pressure was used to study microstructure of these defects. A new local vibrational mode (LVM) was observed in hydrostatically stressed, Si-doped GaAs. Corresponding infrared absorption peak is distinct from the Si[sub Ga] shallow donor LVM peak, which is the only other LVM peak observed in our samples, and is assigned to the Si DX center. Analysis of the relative intensities of the Si DX LVM and the Si shallow donor LVM peaks, combined with Hall effect and resistivity indicate that the Si DX center is negatively charged. Frequency of this new mode provides clues to the structure of this defect. A pressure induced deep donor level in S-doped InP was also discovered which has the properties of a DX center. Pressure at which the new defect becomes more stable than the shallow donor is 82 kbar. Optical ionization energy and energy dependence of the optical absorption cross section was measured for this new effect. Capture barrier from the conduction band into the DX state were also determined. That DX centers can be formed in InP by pressure suggests that DX states should be common in n-type III-V semiconductors. A method is suggested for predicting under what conditions these defects will be the most stable form of the donor impurity.




Compound and Josephson High-Speed Devices


Book Description

This book reviews both the fundamentals and recent advances in analog and digital integrated circuits in compound semiconductors and Josephson junctions. Researchers, engineers, and graduate students who are unfamiliar with the field will find here a complete, unified account of the physical principles, concepts, and design techniques of these devices.




Frontiers of High Pressure Research II


Book Description

Proceedings of the NATO Advanced Research Workshop, Pingree Park, CO, USA, from 10-15 June 2001







New Horizons in Low-Dimensional Electron Systems


Book Description

In Bird of Passage by Rudolf Peierls, we find a paragraph in which he de scribes his Cambridge days in the 1930s: On these [relativistic field theory] problems my main contacts were Dirac, and the younger theoreticians. These included in particular Nevill (now Sir Nevill) Mott, perhaps the friendliest among many kind and friendly people we met then. Professor Kamimura became associated with Sir Rudolf Peierls in the 1950s, when he translated, with his colleagues, Peierls's 1955 textbook, Quantum Theory of Solids, into Japanese. This edition, to which Sir Rudolf himself contributed a preface, benefitted early generations of Japanese solid state physicists. Later in 1974/5, during a sabbatical year spent at the Cavendish Laboratory, Professor Kamimura met and began a long association with Sir Nevill Mott. In particular, they developed ideas for disordered systems. One of the outcomes is a paper coauthored by them on ESR-induced variable range hopping in doped semiconductors. A series of works on disordered systems, together with those on two-dimensional systems, have served as building blocks for Physics of Interacting Electrons in Disordered Systems, in the International Series of Monographs on Physics, coauthored by Aoki and published in 1989 by the Oxford University Press. Soon after Professor Kamimura obtained a D. Sc. in 1959 for the work on the ligand field theory under the supervision ofMasao Kotani, his strong con nections in the international physical community began when he worked at the Bell Telephone Laboratories in 1961/64.