This research examines basic properties of III-V compounds which relate to present or future electronic device requirements. Transport properties are studied, with emphasis on the effects of high fields, and the influence of these effects on specific device configurations is examined. Particular emphasis is placed on the study of heterojunctions, including transport properties, band discontinuities, material properties, lattice matching, and growth conditions, as well as quantum effects.

In this research we are studying the ultimate limitations of electronic transport in silicon and III-V compounds including superlattices and the corresponding potential for new devices, as well as the advantages of including heterolayers in conventional devices. The theoretical approach includes Monte Carlo simulations and explicit solutions of the Boltzmann equation. We are also developing a new algorithm to solve problems of quantum transport in the presence of dissipation.

Our goal is to explore, starting from the analysis of problems in single devices, the influence that quantum phenomena and hot electron effects have on circuit level reliability models, with a focus on issues of scalability and reliability. We take a viewpoint of unification and investigate those mechanisms of electronic transport in conventional devices (such as MOS transistors) that occur for the smallest feature sizes and directly relate to mesoscopic transport effects that are characteristic for nanometer semiconductor structures. Approaching meso scopic nanostructure effects from ``above'' (from the MOS-technology point of view) and conventional scaled silicon devices from ``below'' (from the mesoscopic systems viewpoint) is the central theme of this project.

Ultralow-dimensional structures, such as quantum wires or quantum dots characterized by transverse dimensions below 100 nm, may constitute the next generation of very sophisticated semiconductor devices. This research aims to investigate the potential of these artificial systems for VLSI and high-speed applications. This effort involves the fabrication and characterization of low-dimensional structures, as well as basic studies and modeling of their electronic and transport properties.

This research is theoretical in nature and addresses major transport issues in quantum wires. New phonon resonant effects which indicate superior transport performances in 1-D field effect transistor structures compared to conventional 2-D devices are investigated. Exotic effects such as low-temperature velocity oscillations and nonequilibrium anomalies in the carrier distribution function determined by optic phonon scattering are also studied.

Conception, design, and implementation of an optically pumped, intersubband coupled, quantum-well laser that operates at mid-infrared wavelengths are investigated. This laser shows great promise for becoming a key electronic component in long wavelength telecommunication with potential for applications in molecular infrared spectroscopy, remote sensing, space research, and many other fields. This collaboration is an integrated experimental and theoretical approach to investigate the carrier relaxation channels between subbands in the laser structure.

This is collaborative research between the Institute of Semiconductor Physics at the Ukrainian Academy of Sciences and the University of Illinois on the electronic and transport properties of 2-D ensembles of quantum dots for potential applications in sophisticated forms of highly functional electronic devices. Various transport schemes in 2-D configurations of quantum dots or quantum antidots which could lead to novel nonlinear electrical characteristics are investigated.

The goal of this research is to develop full-band Monte Carlo simulation software for the analysis of hot-electron effects in advanced integrated silicon devices. Besides being used for self-consistent device simulation, the Monte Carlo software will provide calibration for faster simulation tools designed for the solution of the Boltzmann equation in the spherical harmonics expansion approximation or in the scattering matrix formalism. This aspect of the project involves a collaboration with the University of Maryland and Purdue University. For this research, new approaches of technology transfer mechanisms based on the use of distributed computation/visualization on the World Wide Web are being developed.

In order to make full-band Monte Carlo a practical investigation tool, it is important to identify a hierarchy

In the Computational Electronics Laboratory in the Beckman Institute, Professor Umberto Ravaioli (left) and graduate student Brian Winstead (center) and post-doctoral associate Albert Galick discuss the results of a semiconductor device simulation. (Photo: Thompson-McClellan) 1

of models with increasing complexity, so that the most convenient physical formulation can be applied to the problem at hand. This research addresses a comprehensive array of goals to achieve a standardization of the full-band Monte Carlo. The effect of grid refinement strategies in momentum space will be investigated, and alternative approaches to optimize the calculation of momentum trajectories will be compared. Approaches to variance reduction that improve the inherent noise of Monte Carlo simulation are also developed, and hybrid methods involving evolutionary algorithms are investigated.

This research focuses on the development of numerical simulation approaches suitable for the analysis and design of nanostructures. The investigations will address quantum wire and quantum dot structures, with the goal of developing comprehensive physical and numerical models that can explain the results of measurements on experimental nanostructures in a wide range of temperatures. The work will also consider new structures based on modification of existing silicon technology scales into the nanometer range. A major effort will be in the area of 3-D models, to extend previous work to even more realistic situations, and improve the ability to treat extremely large numerical problems efficiently. 1