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Sunday, September 8, 2019

#410 What makes university a research university?

It may come as a surprise, but there seems to be no universally accepted answer to the question what makes the university a research university. The same set of criteria is used pretty much all over the world, but emphasis on what is a truly defining factor vary depending on the local circumstances.


No measure is perfect, no raw numbers can fully define quality of education and research in an institution of higher education. Is it a number of publications, amount of funding, or number of Ph.Ds. graduated annually? In addressing this issue, Carnegie Foundation got it right by using number of doctoral degrees granted per year as a lead criterion distinguishing between R1, R2, and R3 research universities. Why Ph.D. degrees weight so much? Because it is in the Ph.D. process where the educational and research missions of the university come together.


And by the way, another term for the research university is a doctoral university in which research funding is an engine driving a Ph.D. process, and publications are the results of such process and its goal.

Posted by Jerzy Ruzyllo at 02:55 AM | Semiconductors | Link

Sunday, August 25, 2019

#409 Silicon makes MEMS possible

A very distinct class of semiconductor devices is represented by Micro-Electro-Mechanical Systems (MEMS), also referred to as Nano-Electro-Mechanical Systems (NEMS) depending on the size of device features. The electro-mechanical semiconductor devices were conceived as a way to exploit excellent mechanical properties of silicon which allows literally endless possibilities for integration of electronic and mechanical functions within a single material system.


MEMS (Micro-Electro Mechanical System) and NEMS (Nanp-Electro Mechanical System) devices integrate mechanical and electrical functions using somewhat modified, but otherwise standard semiconductor device manufacturing technology. Such functional integration is possible only because silicon, besides advantageous electrical and cost/manufacturing related characteristics, also features outstanding mechanical properties. This combination is unique to silicon and cannot be reproduced using any other material. In broad terms, MEMS/NEMS devices fall into two categories of microsensors and microactuators. In the former case mechanical motion of the parts of the MEMS device caused for instance by acceleration (accelerometers), or pressure (pressure sensors) is converted into electrical signal. In the latter case, MEMS device is converting electrical signal into mechanical motion by engaging micro-motors, micro-gears, and other mechanical parts comprising its structure.

Posted by Jerzy Ruzyllo at 04:21 PM | Semiconductors | Link

Sunday, August 11, 2019

#408 Thin-Film Transistor: unsung hero of transistor technology

A Thin-Film Transistor (TFT) is a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) fabricated using thin-film technology rather than conventional technology which forms MOSFETs on the bulk wafers. Unlike in the case of the bulk MOSFET, where channel is formed in the single crystal semiconductor, the channel in TFTs is most commonly formed using non-crystalline, amorphous semiconductor. By definition then, TFT features inferior to conventional MOSFET electronic properties because of the much higher electron mobility in the single-crystal semiconductor as compared to the amorphous semiconductor.


In spite of their performance limiting features, TFTs are among the most important semiconductor devices primarily because of the role they play in flat panel display technology. Whether it is a Liquid Crystal Display (LCD) or emissive display based on Light Emitting Diodes (LED) the best resolution, highest contrast, and significantly improved addressability is achieved when each pixel in individually powered up by the transistor integrated into the pixel’s structure. Displays incorporating TFTs are known as Active Matrix displays and offer the best rendering of images and colors.

Posted by Jerzy Ruzyllo at 05:34 PM | Semiconductors | Link

Sunday, July 28, 2019

#407 Here comes "quantum"

Quantum computing was alluded to in the blog #402 posted on 3/31/19. In the context of the alternative transistor solutions considered in the last few entries, there is a need to mention quantum transistor. With quantum computing we are venturing beyond a realm of the binary system and conventional computers.


The device used to carry out quantum computing operations is referred to as quantum transistor in spite of the fact that its operation is based on the entirely different principles than the operation of the conventional field-effect transistor for instance. What these two types of drastically different in terms of principles of operation transistors have in common, is the fact that both are constructed using primarily semiconductor materials, and fabricated using methods which rely heavily on semiconductor nanotechnology

Posted by Jerzy Ruzyllo at 12:57 PM | Semiconductors | Link

Sunday, July 14, 2019

#406 Photonic alternative

In another solution, electron as an information carrier is replaced by the photon, representing quantum of light. Photon is more efficient than electron information carrier as it can cover distances in the waveguides with very little losses, which is in stark contrast to electron moving in semiconductors and metals with significant losses.


With short wavelength laser diodes and detectors available, and optical waveguides technology being well develop, a still missing link in this “all photonics” scenario is a high-performance optical transistor needed to turn light “on” and “off”.

Posted by Jerzy Ruzyllo at 11:46 AM | Semiconductors | Link

Sunday, June 16, 2019

#405 MOSFET evolution - alternative solutions

As indicated in the previous blog, solutions concerned with materials and architecture modifications of the MOSFET may not be enough to meet anticipated future needs with regard to the performance of devices designed to carry out logic functions. Therefore, alternative solutions radically departing from the mainstream approaches to transistors’ performance improvements are pursued.


Logic circuits carrying out computational operations, operate based on the binary system needed to code and process information which basically comes to switching the system from one state to another. In electronic devices this function is very efficiently carried out by transistors which turn flow of electrons (current) on and off. The problem is that scattering of electrons moving through the solid accounts for the significant signal losses, and thus, electrons as the carriers of electric charge may not be able to support long-term needs of information processing systems.


One of the solutions being explored is concerned with transistors in which magnetic rather than electric field controls device operation and exploits the fact that in addition to electric charge, electron also features an angular momentum known as electron spin. The spin of the electron can be directed by the magnetic field either up or down. In the sense then, it represents an inherently binary system which spintronics attempts to use in a magnetically sensitive transistor, called a spin transistor, to perform logic functions.

Posted by Jerzy Ruzyllo at 07:17 PM | Semiconductors | Link

Sunday, May 12, 2019

#404 Evolution of the MOSFET

As an "old timer", I follow evolution of the MOSFET (Metal Oxide Semiconductor Field Effect Transistor) since it has began to be a go to transistor configuration. And it changed pretty drastically over the years.


The evolution is proceeding in three distinct areas: gate scaling, materials used, and transistor's architecture. Regarding gate scaling, situation is clear. Over the last 50 years gate length was reduced by three orders of magnitude, i.e. from 10 micrometer to 10 nanometer. And scaling below 10 nm is happening now. How low will it go below 5 nm, remains to be seen.


There are other ways to improve transistor performance. High electron mobility semiconductors used as channel materials are coming to the rescue. May be molybdenum sulfide, or graphene?


Finally, changes in the transistor architecture bring about improved transistor's performance without gate shortening. Transistor architecture goes vertical with FinFET being very likely just the first step. The problem is that all of the above may not be enough to assure long-term growth of computational electronics. That's why alternative to the electric charge based transistors are pursued...

Posted by Jerzy Ruzyllo at 10:40 AM | Semiconductors | Link

Sunday, April 14, 2019

#403 Image sensing relies entirely on semiconductors

The image sensing devices are designed to capture light representing image and to convert it into electrical signal. The image sensors are at the core of any imaging device such as digital still cameras, digital video cameras, mobile devices, medical, surveillance, scientific, and broadcast instrumentation and many others we rely on so heavily in our daily lives.


The message here is that the image sensing devices are operating based on the physical properties of semiconductors and are manufactured using semiconductor materials. As a result, imaging devices constitute an important segment of commercial semiconductor technology. Two the most important types of semiconductor imaging devices are both based on the physical properties of the MOS (Metal-Oxide-Semiconductor) structure. First, involves CCD (Charge Coupled Devices) image sensors. Second, CMOS (Complementary MOS) image sensors. Quite interestingly this is fundamentally the same MOS structure upon which logic cells constituting all important digital integrated circuits are constructed. Equally interesting is the fact that the silicon is a semiconductor material used to fabricate both types of devices.

Posted by Jerzy Ruzyllo at 10:36 AM | Semiconductors | Link

Sunday, March 31, 2019

#402 Microtechnology, nanotechnology... quantum technology

Some of us are not only experiencing current era of nanotechnology (1 nm = 10-9 m) from its onset, but also remember times when microtechnology (1 µm = 10-6 m) was a buzz-term in science and engineering.


If the size related trends in technology evolution were to continue, then picotechnology (1 picometer or pm = 10-12 m) should be their continuation. Let's keep in mind, however,  that the average atom is sized at some 20000 picometers. Thus, the very concept of matter manipulation at the picometer level is beyond the realm of the current understanding of how the world around us works. So, picotechnology understood as a size-based continuation of nanotechnology is not going to happen, at least not in the foreseeable future.


Instead, we are in the process of parting ways with geometrical associations and start using nature of atomic-level physical phenomena related to quantum confinement as a reference. When the size of the piece of the solid is reduced to some 10 nm or below, laws of classical physics (with which we are so comfortable!) are no longer adequately describing properties of this solid and quantum physics (which is escaping our  imagination and intuition) is taking over. At this point the term nanotechnology is no longer adequately describing technological status quo and the term quantum technology is becoming a buzz-term in science and engineering.

Posted by Jerzy Ruzyllo at 05:05 PM | Semiconductors | Link

Sunday, March 17, 2019

#401 Carry it on you, wear it...

Mentioning of sensors (previous blog) brings to mind portability and wearability of the current, and even more so, future generations of electronic and photonic devices. All that is needed is a device (sensor for instance) performing any given function (e.g. counting your steps), battery powering it up, and the means of wireless communication connecting it to the other electronic systems such as your smartphone.


In the light of the developments stressing portability, mobility, and on-the-go accessibility, permanent or temporary integration of ultra-light and ultra-low power, high-end semiconductor-based electronic and photonic devices and systems with clothes we are wearing and with our bodies (including implantation) is an aggressively pursued avenue of growth for semiconductor technology. 


And we are getting there (see examples). Consider smartwatch for instance which for all practical purposes is nothing less than the pretty advanced wearable computer in the form of a wristwatch.


Posted by Jerzy Ruzyllo at 05:54 PM | Semiconductors | Link

›› is the personal blog of Jerzy Ruzyllo. With over 35 years of experience in academic research and teaching in the area of semiconductor engineering (currently holding position of a Distinguished Professor of Electrical Engineering and Professor of Materials Science and Engineering at Penn State University), he has a unique perspective on the developments in this progress driving technical domain and enjoys blogging about it.

With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.

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