Abstract: An n-layer is arranged above a substrate, which can be GaAs, and a p-layer (4) is arranged on the n-layer. The p-layer is separated by a gate electrode into two separate portions forming source and drain. The gate electrode is insulated from the semiconductor material by a gate dielectric. Source/drain contacts are electrically conductively connected with the portions of the p-layer.

Abstract: The invention provides for an alternative and less complex method of manufacturing a bipolar transistor comprising a field plate (17) in a trench (7) adjacent to a collector region (21), which field plate (17) employs a reduced surface field (Resurf) effect. The Resurf effect reshapes the electric field distribution in the collector region (21) such that for the same collector-base breakdown voltage the doping concentration of the collector region (21) can effectively be increased resulting in a reduced collector resistance and hence an increased bipolar transistor speed. The method comprises a step of forming a base window (6) in a first base layer (4) thereby exposing a top surface of the collector region (21) and a part of an isolation region (3). The trench (7) is formed by removing the exposed part of the isolation region (3), after which isolation layers (9,10) are formed on the surface of the trench (7).

Abstract: Provided is a semiconductor device including: a silicon substrate; at least two trenches spaced apart from each other, being in parallel with each other, and being formed by vertically etching the silicon substrate from a surface thereof; an electrically insulating film for burying therein at least bottom surfaces of the trenches; a base region formed in a region of the silicon substrate located between the two trenches; and an emitter region and a collector region formed on portions of side surfaces of the trenches, respectively, the portions of the sides located above the insulating film and formed in the base region.

Abstract: A method for increasing the speed of a bipolar transistor, includes the following steps: providing a bipolar transistor having emitter, base, and collector regions; providing electrodes for coupling electrical signals with the emitter, base, and collector regions; and adapting the base region to enhance stimulated emission to the detriment of spontaneous emission, so as to reduce carrier recombination lifetime in the base region.

Abstract: An integrated circuit package system includes: providing a die attach paddle with interconnection pads connected to a bottom surface of the die attach paddle; connecting a first device to the interconnection pads with a bond wire; connecting a lead to the interconnection pad or to the first device; encapsulating the first device and the die attach paddle with an encapsulation having a top surface; and etching the die attach paddle leaving a recess in the top surface of the encapsulation.

Abstract: A process for forming bipolar junction transistors having a plurality of different collector doping densities on a semiconductor substrate and an integrated circuit comprising bipolar junction transistors having a plurality of different collector doping densities. A first group of the transistors are formed during formation of a triple well for use in providing triple well isolation for complementary metal oxide semiconductor field effect transistors also formed on the semiconductor substrate. Additional bipolar junction transistors with different collector doping densities are formed during a second doping step after forming a gate stack for the field effect transistors. Implant doping through bipolar transistor emitter windows forms bipolar transistors having different doping densities than the previously formed bipolar transistors.

Abstract: A base structure for high performance Silicon Germanium:Carbon (SiGe:C) based heterojunction bipolar transistors (HBTs) with phosophorus atomic layer doping (ALD) is disclosed. The ALD process subjects the base substrate to nitrogen gas (in ambient temperature approximately equal to 500 degrees Celsius) and provides an additional SiGe:C spacer layer. During the ALD process, the percent concentrations of Germanium (Ge) and carbon (C) are substantially matched and phosphorus is a preferred dopant. The improved SiGe:C HBT is less sensitive to process temperature and exposure times, and exhibits lower dopant segregation and sharper base profiles.

Abstract: A semiconductor light-emitting transistor device, including: a bipolar pnp transistor structure having a p-type collector, an n-type base, and a p-type emitter; a first tunnel junction coupled with the collector, and a second tunnel junction coupled with the emitter; and a collector contact coupled with the first tunnel junction, an emitter contact coupled with the second tunnel junction, and a base contact coupled with the base; whereby, signals applied with respect to the collector, base, and emitter contacts causes light emission from the base by radiative recombination in the base.

Abstract: In one embodiment, a method comprises forming an epitaxial layer over a substrate of an opposite conductivity type, the epitaxial layer being separated by a buffer layer having a doping concentration that is substantially constant in a vertical direction down to the buffer layer. A pair of spaced-apart trenches is formed in the epitaxial layer from a top surface of the epitaxial layer down at least into the buffer layer. A dielectric material is formed in the trenches over the first and second sidewall portions. Source/collector and body regions of are formed at the top of the epitaxial layer, the body region separating the source/collector region of the pillar from a drift region of the epitaxial layer that extends from the body region to the buffer layer. An insulated gate member is then formed in each of the trenches adjacent to and insulated from the body region.

Abstract: A semiconductor sensing device in which a sensing layer is exposed to a medium being tested in an area below and/or adjacent to a contact. In one embodiment, the device comprises a field effect transistor in which the sensing layer is disposed below a gate contact. The sensing layer is exposed to the medium by one or more perforations that are included in the gate contact and/or one or more layers disposed above the sensing layer. The sensing layer can comprise a dielectric layer, a semiconductor layer, or the like.

Abstract: A bipolar transistor with very high dynamic performance, usable in an integrated circuit. The bipolar transistor has a single-crystal silicon emitter region with a thickness smaller than 50 nm. The base of the bipolar transistor is made of an SiGe alloy.

Abstract: High frequency performance of (e.g., silicon) bipolar devices (100, 100?) is improved by reducing the extrinsic base resistance Rbx. Emitter (160), base (161) and collector (190) are formed in or on a semiconductor substrate (110). The emitter contact (154) has a portion (154?) that overhangs a portion (1293, 293?) of the extrinsic base contact (129), thereby forming a cave-like cavity (181, 181?) between the overhanging portion (154?) of the emitter contact (154) and the underlying regions (1293, 1293?) of the extrinsic base contact (129). When the emitter contact and the extrinsic base contact are silicided, some of the metal atoms forming the silicide penetrate into the cavity (181, 181?) so that the highly conductive silicided extrinsic base contact extends under the edge of the emitter contact (154?) closer to the base (161, 163) itself, thereby reducing Rbx. Smaller Rbx provides transistors with higher fMAX.

Abstract: The semiconductor device, which provides reduced electric current leakage and parasitic resistance to achieve stable current gain, is provided. A first polycrystalline semiconductor layer is grown on a p-type polycrystalline silicon film exposed in a lower surface of a visor section composed of a multiple-layered film containing a p-type polycrystalline silicon film and a silicon nitride film, while growing the first semiconductor layer on a n-type collector layer, and then the first polycrystalline semiconductor layer is selectively removed.

Abstract: In a GaAs substrate as a semi-insulating substrate, a heterojunction bipolar transistor (HBT) is formed in an element formation region, while an isolation region is formed in an insulating region. The isolation region formed in the insulating region is formed by introducing helium into the same semiconductor layers as the sub-collector semiconductor layer and collector semiconductor layer of the HBT. In an outer peripheral region, a conductive layer is formed to be exposed from protective films and coupled to a back surface electrode. Because a GND potential is supplied to the back surface electrode, the conductive layer is fixed to the GND potential. The conductive layer is formed of the same semiconductor layers as the sub-collector semiconductor layer and collector semiconductor layer of the HBT.

Abstract: A bipolar transistor 120 comprises a substrate 1, a intrinsic base region 11 and an extrinsic base region 12. The intrinsic base region 11 comprises a silicon buffer layer 109 comprised of silicon which is formed on the substrate 1, and a composition-ratio graded base layer 111 which is formed on the silicon buffer layer and comprises silicon and at least germanium and where a composition ratio of the germanium to the silicon varies in a thickness direction of the composition-ratio graded base layer 111. The extrinsic base region 12 comprises an extrinsic base formation layer 113 comprised of silicon which is formed on the substrate and adjacent to the silicon buffer layer. And the thickness of the extrinsic base formation layer 113 is not less than 40 nm.

Abstract: A semiconductor device includes: a GaAs chip; and a resin sealing the GaAs chip. The GaAs chip includes: a p-type GaAs layer; an n-type GaAs layer on the p-type GaAs layer; a metal electrode located on the n-type GaAs layer along an edge of the GaAs chip and to which a positive voltage is applied; a device region located in a central portion of the GaAs chip; a semi-insulating region located between the metal electrode and the device region and extending in the p-type GaAs layer and the n-type GaAs layer; and a connecting portion disposed outside the semi-insulating region and electrically connecting the p-type GaAs layer to the metal electrode.

Abstract: Methods and systems for fabricating integrated pairs of HBT/FET's are disclosed. One preferred embodiment comprises a method of fabricating an integrated pair of GaAs-based HBT and FET. The method comprises the steps of: growing a first set of epitaxial layers for fabricating the FET on a semi-insulating GaAs substrate; fabricating a highly doped thick GaAs layer serving as the cap layer for the FET and the subcollector layer for the HBT; and producing a second set of epitaxial layers for fabricating the HBT.

Abstract: A SiGe bipolar transistor containing substantially no dislocation defects present between the emitter and collector region and a method of forming the same are provided. The SiGe bipolar transistor includes a collector region of a first conductivity type; a SiGe base region formed on a portion of said collector region; and an emitter region of said first conductivity type formed over a portion of said base region, wherein said collector region and said base region include carbon continuously therein. The SiGe base region is further doped with boron.

Abstract: A process for forming bipolar junction transistors having a plurality of different collector doping densities on a semiconductor substrate and an integrated circuit comprising bipolar junction transistors having a plurality of different collector doping densities. A first group of the transistors are formed during formation of a triple well for use in providing triple well isolation for complementary metal oxide semiconductor field effect transistors also formed on the semiconductor substrate. Additional bipolar junction transistors with different collector doping densities are formed during a second doping step after forming a gate stack for the field effect transistors. Implant doping through bipolar transistor emitter windows forms bipolar transistors having different doping densities than the previously formed bipolar transistors.

Abstract: A method of forming a multijunction solar cell includes providing a substrate, forming a first subcell by depositing a nucleation layer over the substrate and a buffer layer including gallium arsenide (GaAs) over the nucleation layer, forming a middle second subcell having a heterojunction base and emitter disposed over the first subcell and forming first and second tunnel junction layers between the first and second subcells. The first tunnel junction layer includes GaAs over the first subcell and the second tunnel junction layer includes aluminum gallium arsenide (AlGaAs) over the first tunnel junction layer. The method further includes forming a third subcell having a homojunction base and emitter disposed over the middle subcell.

Abstract: The present invention provides a highly doped semiconductor layer. More specifically, the present invention provides a semiconductor layer that includes at least two impurities. Each impurity is introduced at a level below its respective degradation concentration. In this manner, the two or more impurities provide an additive conductivity to the semiconductor layer at a level above the conductivity possible with any one of the impurities alone, due to the detrimental effects that would be created by increasing the concentration of any one impurity beyond its degradation concentration.

Abstract: The present invention relates to a microelectronic device having a bipolar epitaxial structure that provides at least one bipolar transistor element formed over at least one field effect transistor (FET) epitaxial structure that provides at least one FET element. The epitaxial structures are separated with at least one separation layer. Additional embodiments of the present invention may use different epitaxial layers, epitaxial sub-layers, metallization layers, isolation layers, layer materials, doping materials, isolation materials, implant materials, or any combination thereof.

Abstract: One or more embodiments relate to a method of making a heterojunction bipolar transistor (HBT) structure. The method includes: forming a partially completed heterojunction bipolar transistor (HBT) structure where the partially completed heterojunction bipolar transistor (HBT) structure includes a silicon layer having an exposed surface and a nitride layer having an exposed surface. The method includes growing a first oxide on the silicon layer and etching the nitride layer using an etchant.

Abstract: A biCMOS device including a bipolar transistor and a Polysilicon/Insulator/Polysilicon (PIP) capacitor is disclosed. A biCMOS device may have a relatively low series resistance at a bipolar transistor. A bipolar transistor may have a desirable amplification rate.

Abstract: A passivation layer of AlN is deposited on a GaN channel HFET using molecular beam epitaxy (MBE). Using MBE, many other surfaces may also be coated with AlN, including silicon devices, nitride devices, GaN based LEDs and lasers as well as other semiconductor systems. The deposition is performed at approximately 150° C. and uses alternating beams of aluminum and remote plasma RF nitrogen to produce an approximately 500 ? thick AlN layer.

Abstract: The invention provides a method for fabricating a heterojunction bipolar transistor with a base connecting region (23), which is formed self-aligned to a base region (7) without applying photolithographic techniques. Further, a collector connecting region (31) and an emitter region (29) are formed simultaneously and self-aligned to the base connecting region (23) without applying photolithographic techniques.

Abstract: Disclosed are apparatus and methods for designing electrical contact for a bipolar emitter structure. The area of an emitter structure (106, 306, 400, 404) and the required current density throughput of an electrical contact structure (108, 308, 402, 406) are determined. A required electrical contact area is determined based on the required current density, and the electrical contact structure is then designed to minimize the required electrical contact area with respect to the emitter structure area.

Abstract: A method of growing nitride semiconductor material and particularly a method of growing Indium nitride is disclosed can increase surface flatness of a nitride semiconductor material and decrease density of V-defects therein. Further, the method can increase light emission efficiency of a quantum well or quantum dots of the produced LED as well as greatly increase yield. The method is also applicable to the fabrications of electronic devices made of nitride semiconductor material and diodes of high breakdown voltage for rectification. The method can greatly increase surface flatness of semiconductor material for HBT, thereby increasing quality of the produced semiconductor devices.

Abstract: Methods of manufacturing a semiconductor device and resulting products. The semiconductor device includes a semiconductor substrate, a hetero semiconductor region hetero-adjoined with the semiconductor substrate, a gate insulation layer contacting the semiconductor substrate and a heterojunction of the hetero semiconductor region, a gate electrode formed on the gate insulation layer, an electric field alleviation region spaced apart from a heterojunction driving end of the heterojunction that contacts the gate insulation layer by a predetermined distance and contacting the semiconductor substrate and the gate insulation layer, a source electrode contacting the hetero semiconductor region and a drain electrode contacting the semiconductor substrate. A mask layer is formed on the hetero semiconductor region, and the electric field alleviation region and the heterojunction driving end are formed by using at least a portion of the first mask layer.

Abstract: A method for manufacturing a semiconductor array, particularly a high-frequency bipolar transistor, is provided, the method includes process steps, so that a dielectric is produced on a mono-crystalline, first semiconductor region of a first conductivity type, a silicide layer is deposited and patterned in such a way that the silicide layer is insulated from the first semiconductor region by the dielectric, and, to form a base region, a second semiconductor region of a second conductivity type is applied to the first semiconductor region and to the silicide layer in such a way that the second semiconductor region lies with a first interface on the first semiconductor region and with a second interface on the silicide layer.

Abstract: An integrated circuit arrangement and fabrication method is provided. The integrated circuit arrangement contains an NPN transistor and a PNP transistor. The PNP transistor contains an emitter connection region and a cutout. The cutout delimits the width of the emitter connection region. The electrically conductive material of the connection region laterally overlaps the cutout.

Abstract: A semiconductor device provided with an emitter layer having a narrowed base contact portion. The semiconductor device includes a collector layer arranged on a semiconductor substrate. A conductive layer is arranged on the collector layer. A silicon film is arranged on the conductive layer. An emitter electrode is arranged on the silicon film. A first film covers the side of the emitter electrode. The silicon film includes a first region contacting the emitter electrode and a second region differing from the first region. A contact surface between the first region and the emitter electrode is located at a level that is higher than that of the lower surface of the first film. At least part of the second region of the silicon film is located between the conductive layer and the first film and is in contact with the conductive layer and the first film.

Abstract: A method and a multijunction solar device having a high band gap heterojunction middle solar cell are disclosed. In one embodiment, a triple-junction solar device includes bottom, middle, and top cells. The bottom cell has a germanium (Ge) substrate and a buffer layer, wherein the buffer layer is disposed over the Ge substrate. The middle cell contains a heterojunction structure, which further includes an emitter layer and a base layer that are disposed over the bottom cell. The top cell contains an emitter layer and a base layer disposed over the middle cell.

Abstract: A method of fabricating a bipolar junction transistor is provided herein. An isolation structure is formed on a first conductive type substrate. A second conductive type deep well is formed in the first conductive type substrate to serve as a collector. Thereafter, a second conductive type well is formed in the substrate and then a first conductive type well is formed in the substrate to serve as a base. A buffer region is formed underneath a portion of the isolation structure and between the base and the second conductive well. The buffer region together with the isolation structure isolates the base from the second conductive type well. A second conductive type emitter and a second conductive type collector pick-up region are selectively formed on the surface of the first conductive type substrate. Thereafter, a first conductive type base pick-up region is selectively formed.

Abstract: A method for fabricating integrable PMOSFET semiconductor structures in a P-doped substrate which are distinguished by a high dielectric strength is provided. In order to fabricate the PMOSFET semiconductor structure, a mask is applied to a semiconductor substrate for the definition of a window delimited by a peripheral edge. An N-doped well is thereupon produced in the P-doped semiconductor substrate by means of high-voltage ion implantation through the window delimited by the mask, the edge zone of said N-doped well reaching as far as the surface of the semiconductor substrate. The individual regions for the source, drain and bulk of the PMOSFET semiconductor structure are then produced in the P-doped inner zone enclosed by the well. The P-doped inner zone forms the drift zone of the PMOSFET structure. Since the drift zone has the weak basic doping of the substrate, the PMOSFET has a high dielectric strength.

Abstract: A transistor epitaxial wafer having: a substrate; an n-type collector layer, a p-type base layer and an n-type emitter layer formed on the substrate in this order; and an n-type InGaAs non-alloy layer having an n-type InGaAs nonuniform composition layer formed on the n-type emitter layer and having an nonuniform indium (In) composition, and an n-type InGaAs uniform composition layer formed on the n-type InGaAs nonuniform composition layer and having a uniform indium (In) composition. The n-type InGaAs nonuniform composition layer has a first layer doped with Si and having a low indium (In) composition, and a second layer formed on the first layer, doped with an n-type dopant except Si, and having an indium (In) composition higher than the first layer.

Abstract: The object of the present invention is to provide a semiconductor device and the manufacturing method thereof which are capable of preventing decrease in the collector breakdown voltage and reducing the collector resistance. The semiconductor device according to the present invention includes: a HBT formed on a first region of a semiconductor substrate; and an HFET formed on a second region of the semiconductor substrate, wherein the HBT includes: an emitter layer of a first conductivity; a base layer of a second conductivity that has a band gap smaller than that of the emitter layer; a collector layer of the first conductivity or a non-doped collector layer; and a sub-collector layer of the first conductivity which are formed sequentially on the first region, and the HFET includes an electron donor layer including a part of the emitter layer, and a channel layer formed under the electron donor layer.

Abstract: A dynamic random access memory (DRAM) cell is described, including a semiconductor pillar on a substrate, a capacitor on a lower portion of a sidewall of the pillar, and a vertical transistor on an upper portion of the sidewall of the pillar. The capacitor includes a first plate in the lower portion of the sidewall of the pillar, a second plate as an upper electrode at the periphery of the first plate, a third plate at the periphery of the second plate electrically connected with the first plate to form a lower electrode, and a dielectric layer separating the second plate from the first and third plates. A DRAM array based on the DRAM cell and a method for fabricating the DRAM array are also described.

Abstract: A hetero-BiMOS injection system comprises a MOSFET transistor formed on a substrate and a hetero-bipolar transistor formed within the substrate. The bipolar transistor can be used to inject charge carriers into a floating gate of the MOSFET transistor. This is done by operating the MOSFET transistor to form an inversion layer in its channel region and operating the bipolar transistor to drive minority charge carriers from the substrate into a floating gate of the MOSFET transistor. The substrate provides a silicon emitter and a silicon germanium containing base for the bipolar transistor. The inversion layer provides a silicon collector for the bipolar transistor.

Abstract: The invention relates to a process of forming a compact bipolar junction transistor (BJT) that includes forming a self-aligned collector tap adjacent the emitter stack and an isolation structure. A base layer is formed from epitaxial silicon that is disposed in the substrate.

Abstract: The invention, in one aspect, provides a method for fabricating a semiconductor device, which includes conducting an etch through an opening in an emitter layer to form a cavity from an underlying oxide layer that exposes a doped tub. A first silicon/germanium (SiGe) layer, which has a Ge concentration therein, is formed within the cavity and over the doped tub by adjusting a process parameter to induce a strain in the first SiGe layer. A second SiGe layer is formed over the first SiGe layer, and a capping layer is formed over the second SiGe layer.

Abstract: The present invention provides an integrated semiconductor device that includes a semiconductor substrate, a first device containing a heterojunction bipolar transistor (HBT) located in a first region of the semiconductor substrate, wherein the HBT includes a base region containing a first portion of a SiGe or SiGeC layer, and a second device located in a second region of the semiconductor substrate, wherein the second device includes an interconnect containing a second portion of the SiGe or SiGeC layer. In a specific embodiment of the present invention, the second device is a memory device including a trench capacitor and a field effect transistor (FET) that are electrically connected together by the second portion of the SiGe or SiGeC layer. Alternatively, the second device is a trench-biased PNPN silicon controlled rectifier (SCR). The present invention also provides a novel reversibly programmable device or a novel memory device formed by a novel trench-biased SCR device.

Abstract: In one aspect of the invention, a method for forming an integrated circuit having an at least substantially doped porous dielectric includes forming a semiconductor device. The semiconductor device includes at least a portion of a semiconductor substrate. The method also includes forming a dielectric layer disposed outwardly from the semiconductor substrate and surrounding at least a portion of the semiconductor device. The dielectric layer includes an at least substantially porous dielectric material doped with at least one dopant. In addition, the method includes forming a contact layer disposed outwardly from the dielectric layer and operable to provide electrical connection to the semiconductor device.

Abstract: A self-aligned bipolar semiconductor device and a fabrication method thereof are provided. After a silicon layer and a collector contact are formed on a buried collector layer, an oxide dummy pattern is formed on the silicon layer to define both an extrinsic base and an intrinsic base. A polycide layer used as the extrinsic base is formed thereon and selectively removed to expose the dummy pattern. After the exposed dummy pattern is removed, an epitaxial layer used as the intrinsic base is grown on both the silicon layer and the polycide layer, and selectively removed from the top of the polycide layer. An oxide layer and a nitride layer are deposited in sequence thereon, and the nitride layer is blanket-etched to form spacers defining an emitter. After a photoresist pattern is formed to mostly cover the oxide layer and partly expose the oxide layer between the spacers over the intrinsic base, the oxide layer is etched by using the photoresist pattern and the spacers as an etch mask.

Abstract: A method for fabricating an HBT is disclosed, wherein successive emitter, base, collector and sub-collector epitaxial layers are deposited on a substrate, with the substrate being adjacent to the sub-collector layer. The epitaxial layers are etched to provide locations for contact metals and emitter, base and contact metals are deposited on the emitter, base and sub-collector epitaxial layers, respectively. A self-alignment material is deposited on the surface of the substrate around the epitaxial layers and a planarization material is deposited on and covers the top surface of the HBT. The planarization material is then etched so it has a planar surface about the same level as the surface of the self-alignment material and the contact metals protrude from the planar surface. The planar metals are then deposited over the protruding portions of the contact metals.

Abstract: A polymer coating material is disposed at a surface of a semiconductor substrate, superimposing a readable mark formed thereupon. A perimeter of the coating material is configured to correspond approximately with a perimeter of the mark, and a thickness of the coating material is configured to be relatively conformal with the surface of the substrate. The mark remains readable through the coating material throughout manufacturing, reliability testing, and normal use. A substrate so formed may constitute a portion of an assembly and/or system (e.g., computer system). Throughout manufacturing, reliability testing and normal use, a readable mark provides product identification, traceability, and other benefits.

Abstract: A bipolar transistor formed in a substrate includes a collector, a base layer above the collector, where the base layer includes a base that is monocrystalline, and an emitter layer that is monocrystalline and above the base, where the emitter layer includes silicon or silicon-germanium. An intermediate layer is above the base layer and below the emitter layer. The intermediate layer includes silicon carbide. The intermediate layer is grown epitaxially and is etchable in a dry plasma relative to the emitter layer.

Abstract: A bipolar transistor having a base electrode of an air bridge structure is simplified in structure and enhanced in the degree of freedom of a contact position of a base wiring line with the base electrode. The bipolar transistor has a semiconductor mesa portion having a base layer formed on an upper face thereof, and a base electrode contacts with the base layer and has a floating extension which extends from the semiconductor mesa portion to a space on the outer side with respect to the semiconductor mesa portion. The floating extension is used as a contact portion for a base wiring line to the base electrode.

Abstract: A method for making a heterojunction bipolar transistor includes the following steps: forming a heterojunction bipolar transistor by depositing, on a substrate, subcollector, collector, base, and emitter regions of semiconductor material; the step of depositing the subcollector region including depositing a material composition transition from a relatively larger bandgap material nearer the substrate to a relatively smaller bandgap material adjacent the collector; and the step of depositing the collector region including depositing a material composition transition from a relatively smaller bandgap material adjacent the subcollector to a relatively larger bandgap material adjacent the base.

Abstract: Disclosed are an improved hetero-junction bipolar transistor (HBT) structure and a method of forming the structure that incorporates a silicon-germanium emitter layer with a graded germanium profile. The graded germanium concentration creates a quasi-drift field in the neutral region of the emitter layer. This quasi-drift field induces valence bandgap grading within the emitter layer so as to accelerate movement of holes from the base layer through the emitter layer. Accelerated movement of the holes from the base layer through the emitter layer reduces emitter delay time and thereby, increases the cut-off frequency (fT) and the maximum oscillation frequency (fMAX) of the resultant HBT.