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Topic: Heterojunction bipolar transistor

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	Process for fabricating heterojunction bipolar transistor with low base resistance - Patent 4617724
		Heterojunction bipolar transistors, in which the emitter bandgap is wider than the base bandgap, have the advantage of higher emitter efficiency since holes (minority carriers for the emitter) flowing from the base to emitter are blocked by the higher barrier in the valence band (cf.
		Furthermore, in a double heterojunction bipolar transistor, the collector layer may be used as an emitter and the emitter layer may be used as a collector.
		A conductive substrate may be used in the bipolar transistor by providing a collector electrode to the collector layer, usually on the side of the substrate opposite to the base and emitter layers.
	www.freepatentsonline.com /4617724.html (5523 words)

	Bipolar junction transistor - Wikipedia, the free encyclopedia
		The symbol of an NPN Bipolar Junction Transistor.
		NPN transistors are commonly operated with the emitter at ground and the collector connected to a positive voltage through an electric load.
		The bipolar (point-contact) transistor was invented in December 1947 at the Bell Telephone Laboratories by John Bardeen and Walter Brattain under the direction of William Shockley.
	en.wikipedia.org /wiki/Bipolar_junction_transistor (3152 words)

	Heterojunction bipolar transistor - Patent 5198689
		A heterojunction bipolar transistor as claimed in claim 1, further comprising a metallic film selectively formed on said emitter layer, and said emitter electrode is formed on said metallic film.
		A heterojunction bipolar transistor as claimed in claim 10, further comprising a metallic film formed on each of said emitter and collector layers through said first and second contact holes, and wherein said emitter electrode and said collector electrode are formed on said metallic films formed on said exposed emitter and collector layers, respectively.
		Recently, heterojunction bipolar transistors of two different types have been proposed, one of which is a wide band gap emitter type heterojunction bipolar transistor, and the other of which is a narrow band gap base type heterojunction bipolar transistor.
	www.freepatentsonline.com /5198689.html (2873 words)

	United States Patent: 5,304,816 (Site not responding. Last check: 2007-10-29)
		Transistors according to the invention typically will have an operating frequency in the range 100 GHz-1THz, and can be advantageously used in many areas of technology, e.g., high speed computing or communications.
		Therefore, prior art ballistic HBTs are typically designed to minimize.tau..sub.B. This generally involves maximizing carrier velocity through choice of low effective mass minority carriers (almost invariably resulting in the choice of n-p-n III/V transistors), and through choice of a design that exhibits a relatively large value of the parameter.DELTA., the injection energy.
		The figure shows, however, that the transistor is active up to frequencies of about 2.pi.f.sub.T. The analysis revealed that the current gain is largely damped away by the parasites (although a trace of the peak is clearly seen near f.tau..sub.B.about.1), and that the unilateral power gain U in the region between the two peaks in.vertline.U.vertline.
	www.ee.sunysb.edu /~serge/pat18.html (2872 words)

	United States Patent: 5,329,144 (Site not responding. Last check: 2007-10-29)
		The disclosed novel heterojunction bipolar transistor, to be referred to as the enhanced diffusion transistor (EDT), comprises a base of composition selected such that the base bandgap narrows from emitter towards collector in substantially step-wise fashion, resulting in N (N.gtoreq.2) substantially flat levels in the base bandgap.
		The coherent transistor employs the base transit angle and therefore is much less susceptible to the parasitic damping than previous proposals utilizing the collector transit angle.
		Although a transistor with CGB is not a EDT according to the instant invention, I have discovered that a transistor of the former type offers the possibility of enhanced high frequency performance in a region of the parameter space that is typically not of interest for prior art CGBs.
	www.ece.sunysb.edu /~serge/pat22.html (2714 words)

	HITACHI GLOBAL : News Releases from Headquarters : Dec 5, 2001
		Bipolar CMOS (BiCMOS), a combination of the ultra-high-speed HBT and the mid-to-low speed signal processing CMOS (Complementary Metal-Oxide Semiconductor), is currently considered a viable solution to the above-mentioned requirement, and research is being focused on this device.
		Improvement in transistor operating speed: A self-aligned SiGeC HBT with low parasitic resistance and low parasitic capacitance was fabricated using a high-quality base layer of SiGeC containing 0.4% carbon, and high-speed high-frequency performances of 124-GHz cutoff frequency and 174-GHz maximum oscillation frequency were achieved.
		High heat-treatment tolerance of SiGeC HBT: Diffusion of the impurity (boron) in the base can be suppressed by adding C to the base layer of the bipolar transistor, and the thickness of the base layer can be reduced even though high-temperature heat treatment is conducted.
	www.hitachi.com /New/cnews/E/2001/1205a/index.html (707 words)

	Heterojunction bipolar transistor and method of manufacturing - Patent 6107151 (via CobWeb/3.1 planetlab2.tamu.edu) (Site not responding. Last check: 2007-10-29)
		Thus, the qualification of HBT structures grown with OMVPE using carbon as the base dopant has not been as successful as that grown with MBE using Be as the base dopant.
		According to the present invention, a combination of techniques are employed in the growth of GaAs doped with Zn in HBT structures to inhibit the substitutional-interstitial diffusion mechanism, thus improving the reliability of the HBT structures.
		Therefore, according to the present invention, an HBT structure with Zn base doping is grown with OMVPE using a combination of techniques to control the diffusion characteristics of Zn and which will exhibit superior performance and reliability than that compared to a HBT structure using carbon as the p-type base doping material.
	www.freepatentsonline.com.cob-web.org:8888 /6107151.html (4366 words)

	InP-Heterojunction Bipolar Transistor Group (Site not responding. Last check: 2007-10-29)
		HBTs have excellent uniformity, the critical dimensions are in the vertical layer structure and are therefore well defined during wafer growth.
		We are using an in-house fabricated self-aligned InP/InGaAs single-heterojunction bipolar transistors (SHBT) for the implementation of the high-speed circuits.
		We are using a mesa-isolated self-aligned InP/InGaAs-Hetero-Bipolar Transistor (HBT) technology with a minimum emitter size of 1.0x5µm2 for the implementation of ultrafast electronic circuits, such as wideband amplifiers, multiplexers, photo receivers and PLLs in clock-recovery circuits.
	www.ife.ee.ethz.ch /hbt/research.html (3188 words)

	Bipolar junction transistor (Site not responding. Last check: 2007-10-29)
		NPN A bipolar junction transistor (BJT) is a type of transistor, an amplifying or switching device constructed of doped semiconductor.
		Structure and use of npn transistor The diagram opposite is a schematic representation of an npn transistor connected to two voltage sources.
		A transistor is said to operate in the "cut off" regime when the base-emitter voltage is too small for any significant current to flow.
	bipolar-junction-transistor.iqnaut.net (756 words)

	Dr. Shabbir A. Bashar's Ph.D. Thesis - Chapter 2, Section 4
		The band energy diagram for such an emitter-base heterojunction, before and after the two materials are brought into contact, is depicted in Figure 2.4a and b respectively.
		The operating principle of a (n-p-n) bipolar transistor consists of electron injection from the emitter into the base and their subsequent collection by the collector.
		Figure 2.5 shows the energy band structure of an N-p-n HBT with wide-gap emitter, with the various current components, and the hole repelling effect of the additional energy gap in the emitter.
	www.betelco.com /sb/phd/ch2/c24.html (1740 words)

	Lighthearted Transistor: Electronic workhorse moonlights as laser: Science News Online, Nov. 20, 2004 (Site not responding. Last check: 2007-10-29)
		Transistors have long served as the building blocks of microelectronics.
		The transistor laser is "a major technology breakthrough in high-speed optoelectronics," comments K.C. Wang of HR Laboratories in Malibu, Calif.
		Such a transistor consists of layers of exotic semiconductor compounds, such as gallium arsenide, stacked on a microchip.
	www.sciencenews.org /articles/20041120/fob3.asp (515 words)

	Heterojunction bipolar transistor - Wikipedia, the free encyclopedia
		The heterojunction bipolar transistor (HBT) is an improvement of the bipolar junction transistor (BJT) that can handle signals of very high frequencies up to several hundred GHz.
		The principal difference between the BJT and HBT is the use of differing semiconductor materials for the emitter and base regions, creating a heterojunction.
		A pseudomorphic heterojunction bipolar transistor developed at the University of Illinois at Urbana-Champaign, built from indium phosphide and indium gallium arsenide and designed with compositionally graded collector, base and emitter, was demonstrated to run at a speed of 710 gigahertz.
	en.wikipedia.org /wiki/Heterojunction_bipolar_transistor (363 words)

	NCSR - Heterojunction Bipolar Transistor
		The HBT is an active bipolar device which incorporates a heterojunction between a wide bandgap semiconductor and narrow bandgap semiconductor, some common materials used are:
		The SHBT has a single heterojunction where the emitter is the wide bandgap material, this allows heavy doping of the base for reduced base resistance while the emitter is more lightly doped reducing the capacitance and improving the high frequency performance.
		The DHBT (Double Heterojunction Bipolar Transistor) has a wide bandgap collector and emitter, allowing the same advantages of the SHBT, with the additional improvement of increased breakdown voltage and decreased minority carrier injection from the base to the collector in saturation mode.
	www.onr.navy.mil /sci_tech/31/312/ncsr/devices/hbt.asp (350 words)

	AlGaAs or InGaP low turn-on voltage GaAs-based heterojunction bipolar transistor - US Patent 6917061 (Site not responding. Last check: 2007-10-29)
		Heterojunction bipolar transistor capable of restraining the conductivity modulation of the ballast layer
		A heterojunction bipolar transistor is provided that has a reduced turn-on voltage threshold.
		The thickness of the emitter layer if utilized is kept to a minimum to reduce the associated space charge recombination current in the heterojunction bipolar transistor.
	www.patentstorm.us /patents/6917061.html (235 words)

	ECE Alumni News - Room-temperature transistor laser is a step closer to commercialization
		“We have shown that the transistor laser, even in its early state of development, is capable of room-temperature operation at a speed of three gigahertz,” said Holonyak Jr., John Bardeen Chair Professor in ECE and Physics.
		Feng’s research on heterojunction bipolar transistors has produced the world’s fastest bipolar transistor, a device that operates at a frequency of 600 gigahertz or more, and is a natural platform on which to develop a transistor laser.
		At that time, the transistor laser had to be chilled with liquid nitrogen to minus 73 degrees Celsius.
	www.ece.uiuc.edu /alumni/w05-06/room-temp-transistors.html (575 words)

	New light-emitting transistor could revolutionize electronics industry
		Graduate student Walid Hafez fabricated the light-emitting transistor in the university's Micro and Nanotechnology Laboratory.
		Unlike traditional transistors, which are built from silicon and germanium, the light-emitting transistors are made from indium gallium phosphide and gallium arsenide.
		Although the recombination process is the same as that which occurs in light-emitting diodes, the photons in light-emitting transistors are generated under much higher speed conditions.
	www.eurekalert.org /pub_releases/2004-01/uoia-nlt122903.php (593 words)

	Silicon:germanium-based mixed-signal technology for optimization of wired and wireless telecommunications
		Scaling limits of silicon-based bipolar transistors have been encountered, confining further performance gains by traditional means, but cost considerations favor the continued use of silicon-derived technology solutions.
		Exploiting newly developed techniques for low-temperature silicon epitaxy [13] and the established theory for bandgap engineering [14], the silicon:germanium-alloy-based heterojunction bipolar transistor (HBT) was developed at IBM [7, 15].
		The SiGe HBT is now formed after the preponderance of CMOS fabrication has been completed, effectively isolating the bipolar process from the many changes in CMOS process integration and thermal cycles from generation to generation.
	www.research.ibm.com /journal/rd/443/meyerson.html (6985 words)

	Heterojunction bipolar transistor - US Patent 5001534 (Site not responding. Last check: 2007-10-29)
		A scalable and relatively easily manufacturable heterojunction bipolar transistor (HBT) comprises a thin (exemplarily 5-25 nm) emitter layer that serves as an etch stop layer and that furthermore passivates the extrinsic base region.
		The portion of the emitter layer that overlies the extrinsic base region is essentially fully depleted at all bias voltages in the normal operating range of the transistor.
		Use of the novel technique makes possible a further embodiment of the inventive HBT, wherein base contact is made by means of Be implantation into the emitter layer.
	www.patentstorm.us /patents/5001534.html (206 words)

	New material structure produces world's fastest transistor
		With their pseudomorphic heterojunction bipolar transistor, the researchers have demonstrated a speed of 604 gigahertz –; the fastest transistor operation to date.
		They describe the pseudomorphic HBT concept, and discuss the transistor’s high-speed operation, in the April 11 issue of the journal Applied Physics Letters.
		The goal of a terahertz transistor was not possible using the previous device structure, Feng said.
	www.news.uiuc.edu /news/05/0411transistor.html (328 words)

	Bipolar transistor having base region with coupled delta layers (US5965931)
		A bipolar transistor includes multiple coupled delta layers in the base region between the emitter and collector regions to enhance carrier mobility and conductance.
		The delta layers can be varied in number, thickness, and dopant concentration to optimize desired device performance and enhanced mobility and conductivity vertically for emitter to collector and laterally parallel to the delta-doped layers.
		The transistors can be homojunction devices or heterojunction devices formed in either silicon or III-V semiconductor material.
	www.delphion.com /details?pn=US05965931__ (320 words)

	High-Temperature Transistor (321)
		Such transistors may also be used to control the power delivered to motors in future electric cars, eliminate the need for expensive and heavy cooling systems in space electronics, allow electric motors to replace hydraulic systems, and permit devices to be packaged more closely together in high-temperature digital circuits.
		As in all bipolar transistors, the HBT consists of an emitter, where the input current enters the transistor; a collector, where the output current leaves the device; and a base, which controls current amplification.
		While the bandgap ratio of GaN/4H-SiC HBT is not as favorable as in GaN/6H-SiC, they did produce workable results: this model exhibited a current gain of 15 at room temperature and 3 at 300°C.
	www.mdatechnology.net /techsearch.asp?articleid=321 (867 words)

	Room-temperature transistor laser is step closer to commercialization
		"We have shown that the transistor laser, even in its early state of development, is capable of room-temperature operation at a speed of 3 gigahertz," said Nick Holonyak Jr., a John Bardeen Chair Professor of Electrical and Computer Engineering and Physics at Illinois.
		Room-temperature transistor lasers "could facilitate faster signal processing, large capacity seamless communications, and higher performance electrical and optical integrated circuits," said Milton Feng, the Holonyak Chair Professor of Electrical and Computer Engineering at Illinois.
		The Illinois researchers first reported the demonstration of a light-emitting transistor in the Jan. 5, 2004, issue of Applied Physics Letters.
	www.eurekalert.org /pub_releases/2005-09/uoia-rtl091905.php (526 words)

	ECS EPrints Service - Non-selective growth of SiGe heterojunction bipolar transistor layers at 700C with dual control ... (Site not responding. Last check: 2007-10-29)
		Non-selective growth of SiGe heterojunction bipolar transistor layers at 700C with dual control of n and p type dopant profiles
		This paper describes the growth of the collector, base and emitter layers of a SiGe HBT in a single epitaxy process.
		A non-selective SiGe heterojunction bipolar transistor growth process at 700C has been developed, which combines n-type doping for the Si collector, p-type doping for the SiGe base and n-type doping for the Si emitter cap.
	eprints.ecs.soton.ac.uk /11170 (296 words)

	SiGe Introduction
		The heart of SiGe technology is a SiGe heterojunction bipolar transistor (HBT), which offers advantages over both conventional silicon bipolar and silicon CMOS for implementation of communications circuits.
		A SiGe HBT is similar to a conventional Si bipolar transistor except for the base.
		A common layer stack is used for both the HBT base and the FET polysilicon gates, thus reducing the number of process steps and mask counts.
	www.eng.auburn.edu /~guofu/sige_intro.htm (1293 words)

	CO801: Semiconductor Device Physics: Courselet 4. Bipolar Junction Transistors
		We examine the bipolar transistor current gain and deviations of the electrical characteristics from the ideal device characteristics.
		Next, polysilicon emitter bipolar transistor and heterojunction bipolar transistor (HBT) structures are described.
		Finally, we describe the high-frequency limitations of bipolar transistors and present their circuit models.
	www.semizone.com /webcast/product-access?product_id=801 (200 words)

	Room-temperature tranisitor laser is step closer to commercialization
		CHAMPAIGN, Ill. — Researchers at the University of Illinois at Urbana-Champaign have demonstrated the room-temperature operation of a heterojunction bipolar transistor laser, moving it an important step closer to commercialization.
		“We have shown that the transistor laser, even in its early state of development, is capable of room-temperature operation at a speed of 3 gigahertz,”; said Nick Holonyak Jr., a John Bardeen Chair Professor of Electrical and Computer Engineering and Physics at Illinois.
		Room-temperature operation is ultimately required for large-scale commercial applications, said Holonyak, who also is a professor in the university’s Center for Advanced Study, one of the highest forms of campus recognition.
	www.news.uiuc.edu /news/05/0926transistorlaser.html (574 words)

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