Resonant Tunneling Based Devices with Memory Applications�

As integrated circuit technology approaches its theoretical limits in Bipolar Junction and MOS device density, the ability to achieve greater circuit density can only be obtained by the developement of new electronic devices. The limits of present Bipolar Junction and MOS devices are due to the domination of quantum mechanical effects as the device dimensions become smaller thus preventing the device from operating in the manner for which it was designed. It is only natural that a device that operates on the basis of quantum effects would be the choice for denser circuitry. A quantum mechanical effect that can be used to make devices of interest is electron tunneling of which resonant tunneling is a special phenomena that exists in certain structures in which tunneling exists. Resonant tunneling is of special interest due to a region of negative differential resistance (NDR) in the current-voltage characteristics which will be shown in Chap. 2. This NDR makes a resonant tunneling device useful in a number of applications including: high frequency oscillators, multi leveled logic, analog to digital converters, infrared laser amplifiers, infrared optical detectors, and memory cells. In chapter II the physics of a double barrier resonant tunneling diode (RTD) is dicussed. The transmission coefficient is derived and the current-voltage characteristics of a double barrier RTD are discussed. Some design considerations for the RTD along with the material used to build these devices are discussed. In chapter III resonant tunneling devices are reviewed. Switching limits and frequency limits of resonant tunneling diodes are also discussed. In chapter IV a SPICE model for a resonant tunneling diode is presented and a new resonant tunneling diode memory cell is presented and analyzed. Finally in chapter V conclusions are drawn about the memory structure presented and suggestions for further research are made.Electrical Engineerin

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4 m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5 m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 yr, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit