Sat Nov 2, 2019, 03:49 PM

New Transistor Breakthrough

"In 1947, the first transistor, a bipolar junction transistor (BJT), was invented in the Bell Laboratory and has since led to the age of information technology. In recent decades, there has been a persistent demand for higher frequency operation for a BJT, leading to the inventions of new devices such as heterojunction bipolar transistors (HBT) and hot electron transistors (HET). The HBTs have enabled terahertz operations, but their cut-off frequency is ultimately limited by the base transit time; for the HETs, the demand of a thin base without pinholes and with a low base resistance usually causes difficulties in material selection and fabrication.

Recently, researchers have proposed graphene as a base material for transistors. Because of the atomic thickness, the graphene base is almost transparent to electron transport, leading to a negligible base transit time. At the same time, the remarkably high carrier mobility of graphene will benefit the base resistance compared with a thin bulk material. Graphene-based transistors (GBTs) generally use a tunnel emitter that emits an electron through an insulator. However, the emitter potential barrier height seriously limits the cut-off frequency. Theoretical study has indicated that a Schottky emitter may solve this potential barrier limitation.

A team of researchers at the Institute of Metal Research, Chinese Academy of Sciences, has built the first graphene-based transistor with a Schottky emitter, which is a silicon-graphene-germanium transistor. Using a semiconductor membrane and graphene transfer, the team stacked three materials including an n-type top single-crystal Si membrane, a middle single-layer graphene (Gr) and an n-type bottom Ge substrate.

Compared with the previous tunnel emitters, the on-current of the Si-Gr Schottky emitter shows the maximum on-current and the smallest capacitance, leading to a delay time more than 1,000 times shorter. Thus, the alpha cut-off frequency of the transistor is expected to increase from about 1 MHz by using the previous tunnel emitters to above 1 GHz by using the current Schottky emitter. THz operation is expected using a compact model of an ideal device. The electrical behavior and physical activity of the working transistor are discussed in detail in the published paper in Nature Communications."

The link won't work.
It's from the Chinese Academy of Science.

So, what the hell does this mean?

"Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency (THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the ITU-designated band of frequencies from 0.1 to 30 terahertz (THz). One terahertz is 1012 Hz or 1000 GHz. Wavelengths of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm (or 100 μm). Because terahertz radiation begins at a wavelength of one millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves, especially in astronomy.

Tremendously high frequency
Frequency range
0.3 THz to 3 THz
Wavelength range
1 mm to 100 μm

Terahertz waves lie at the far end of the infrared band, just before the start of the microwave band.
Terahertz radiation can penetrate thin layers of materials but is blocked by thicker objects. THz beams transmitted through materials can be used for material characterization, layer inspection, and as an alternative to X-rays for producing high resolution images of the interior of solid objects.

Terahertz radiation occupies a middle ground between microwaves and infrared light waves known as the “terahertz gap”, where technology for its generation and manipulation is in its infancy. It represents the region in the electromagnetic spectrum where the frequency of electromagnetic radiation becomes too high to be measured digitally via electronic counters, so must be measured by proxy using the properties of wavelength and energy. Similarly, the generation and modulation of coherent electromagnetic signals in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques."

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Reply New Transistor Breakthrough (Original post)
wonderwarthog Nov 2019 OP
fools_gold Nov 2019 #1
wonderwarthog Nov 2019 #3
It Guy Nov 2019 #2
wonderwarthog Nov 2019 #4

Response to wonderwarthog (Original post)

Sat Nov 2, 2019, 06:01 PM

1. Amazingly, even though it's been over fifty years

since I studied that stuff, I actually understood some of that. Well, a little bit anyway.

Well, actually, a tiny little bit.

At least I understood some of the words!

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Response to fools_gold (Reply #1)

Sat Nov 2, 2019, 06:13 PM

3. Same here!

In training, I was hungry and my mind soaked it up like a sponge, and my excellent instructors imparted it in such a way that I was able to understand. My main instructor was a retired General Electric engineer, the president of the school was an Army Signal Intelligence School graduate in the 50's, he later was a consultant for G.E. in Korea and later in Vietnam.

But, that was 20 years ago. I am making an effort to refresh my memory!

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Response to wonderwarthog (Original post)

Sat Nov 2, 2019, 06:08 PM

2. This was a poorly written article.

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Response to It Guy (Reply #2)

Sat Nov 2, 2019, 06:15 PM

4. Why?

It was translated from Chinese, perhaps that is the problem?

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