Sherra E. Kerns

A multimechanism model for photon generation by silicon junctions in avalanche breakdown

Light emission from three device types ((1) commercial silicon JFETs, (2) bipolar transistors, and (3) a custom diode) with p-n junctions biased in controlled avalanche breakdown, has been measured over the photon energy range 1.4-3.4 eV, Previously published models are compared with these data to elucidate the mechanisms responsible for avalanche light emission in silicon. A multimechanism model fitting measured spectra and spectra measured by other researchers is presented and justified. The success of the model indicates that indirect recombination of electrons and holes is the dominant emission mechanism below the light intensity peak (/spl sim/1.8-2.0 eV), that indirect intraband recombination dominates at intermediate energies up to /spl sim/2.3 eV, and that direct interband recombination between high-field populations of carriers near k=0 dominates above /spl sim/2.3 eV. For junctions with overlayer passivation, an interference model must be applied to model measured spectra.

The Olin curriculum: thinking toward the future

In 1997, the F. W. Olin Foundation of New York established the Franklin W. Olin College of Engineering, Needham, MA, with the mission of creating an engineering school for the 21st century. Over the last five years, the college has transformed from an idea to a functioning entity that admitted its first freshman class in fall 2002. This paper describes the broad outlines of the Olin curriculum with some emphasis on the electrical and computer engineering degree. The curriculum incorporates the best practices from many other institutions as well as new ideas and approaches in an attempt to address the future of engineering education.

Comparison of contactless measurement and testing techniques to a all-silicon optical test and characterization method

The rapid improvement in performance and increased density of electronic devices in integrated circuits has provided a strong motivation for the development of contactless testing and diagnostic measurement methods. This paper first reviews existing contactless test methodologies and then compares these with an all-silicon contactless testing approach that has been recently developed and demonstrated. This cost-effective approach utilizes silicon-generated optical signals and has the advantages of easy test setup, low equipment cost, and noninvasiveness over existing contactless test and measurement methods.

Analysis of electroluminescence spectra of silicon and gallium arsenide p–n junctions in avalanche breakdown

We present a generalized study of light emission from reverse biased p–n junctions under avalanche breakdown conditions. A model is developed based on direct and indirect interband processes including self-absorption to describe measured electroluminescence spectra. This model was used to analyze experimental data for silicon (Si) and gallium arsenide p–n junctions and can be extended to several types of semiconductors regardless of their band gaps. This model can be used as a noninvasive technique for the determination of the junction depth. It has also been used to explain the observed changes of the Si p–n junction electroluminescence spectra after fast neutron irradiation. In particular, it is demonstrated that the neutron irradiation affects both the semiconductor and the overlying passivation oxide layer.

Switch-level simulation of total dose effects on CMOS VLSI circuits

The effects of radiation exposure on the performance of CMOS integrated circuits are difficult to predict and to simulate due to the bias-dependent device parameter shifts. Simulation methodologies for identification of failure mechanisms and performance estimation are developed. These simulation algorithms are implemented in the PARA simulator for switch-level simulation of radiation effects. Simulation results for test circuits are presented that prove that accurate estimations are possible without CPU-intensive simulation programs. >

Analyses of electroluminescence spectra of silicon junctions in avalanche breakdown using an indirect interband recombination model

Light emission from a p-n junction biased in avalanche breakdown has been modeled over the range 1.4–3.4 eV. The model emphasizes indirect interband processes and Si self-absorption. Comparisons between measured and simulated spectra for sample junctions from multiple devices demonstrate that the model is simple, accurate, and consistent with fundamental physical device characteristics.

Simulation of gallium arsenide electroluminescence spectra in avalanche breakdown using self-absorption and recombination models

Light emission from gallium arsenide (GaAs) p–n junctions biased in avalanche breakdown have been modeled over the range of 1.4–3.4 eV. The model emphasizes direct and indirect recombination processes and bulk self-absorption. Comparisons between measured and simulated spectra for sample junctions from custom and commercially fabricated GaAs devices demonstrate that the model is simple, accurate, and consistent with fundamental physical device theory. The model also predicts the junction depth with accuracy.

Statistical degradation analysis of digital CMOS IC's

A statistical switch-level simulator, based on interval and statistical analysis techniques, that simulates the effects of fabrication process fluctuations and environmental effects on digital CMOS integrated circuits is presented. The simulator is computationally very cost-effective compared to conventional Monte Carlo simulators, yet produces results with equal accuracy. The simulator enables analysis of the sensitivity of critical function and performance levels to a variety of parameter variations, thus providing a basis for establishing correspondence between process control, yield, and reliability. >

Circuit technique for threshold voltage stabilization using substrate bias in total dose environments

Radiation tolerance of CMOS circuits to total dose can be improved by adjusting the p-substrate voltage to keep the n-channel threshold voltage above a minimum value. This paper presents a circuit design, implemented on an IC and on a breadboard, for dynamically adjusting the substrate voltage. Experimental results clearly show that devices with threshold voltage stabilization exhibit longer lifetime as compared to those without the stabilization circuit.

Special session — A war of words: Using sticky language to effect change in engineering education

Reform in engineering education requires not only identifying what needs to change, but also understanding implicit barriers to change and the tools that can help overcome them. Language is an excellent example of such a barrier, and of such a tool. For example, engineering educators sometimes refer to “the basics” (math, science, and engineering science) thereby assigning those topics a privileged position in the engineering canon; the same educators will sometimes use the term “soft” to deflate certain qualitative critical thinking, creative, and communications skills, thereby assigning them lower status-and less air time-in the education of student engineers. These examples demonstrate the ability of language to obstruct change, and also suggest that the careful choice of memorable or “sticky” locutions can provide reformers with a powerful means of reframing the debate. In this special session we examine the use of language in the resistance to and promotion of change, and identify promising locutions that can help transform engineering education.