Abstract: Provided is a method of heating a semiconductor substrate having a surface of a III-V compound semiconductor containing phosphorus as a group V constituent element. The method comprises the steps of: (a) providing an alloy in a heating furnace, the alloy including tin, indium, and phosphorus as main constituents; and (b) raising a temperature of the article in an atmosphere containing vapor of phosphorus supplied from the alloy.

Abstract: A process fabricates a vertical structure high carrier mobility transistor on a substrate of crystalline silicon doped with impurities of the N type, the transistor having a collector region located at a lower portion of the substrate.

Abstract: A high performance SiGe HBT that has a SiGe layer with a peak Ge concentration of at least approximately 20% and a boron-doped base region formed therein having a thickness. The base region includes diffusion-limiting impurities substantially throughout its thickness, at a peak concentration below that of boron in the base region. Both the base region and the diffusion-limiting impurities are positioned relative to a peak concentration of Ge in the SiGe layer so as to optimize both performance and yield.

Abstract: A heterojunction bipolar transistor is presented, comprising a substrate having formed thereon a heterojunction bipolar transistor layer structure, and including an emitter layer. The emitter layer includes a strained, n-doped compound of indium arsenic and phosphorus. The transistor further comprises, between the substrate and emitter layer, a subcollector layer, a collector layer, a base layer, and an optional spacer layer. The emitter layer may include a graded portion. A contact layer is formed on the emitter layer to provide contacts for the device.

Abstract: The invention relates to a method for producing bipolar transistors with the aid of selective epitaxy for producing a collector and base. The inventive method is advantageous in that the area of the base is widened by the isotropic etching of the conductive layer or by the oxidation of the conductive layer and by the subsequent removal of the oxide layer. This widening of the area of the base prevents the occurrence of short-circuits between the emitter and the collector during the subsequent production of the base.

Abstract: A heterojunction bipolar transistor has a stack comprised of a base layer, an emitter layer and a ballast layer made of AlGaAs. The emitter layer is comprised of a single layer or a multiplicity of layers, and at least one of which is comprised of a material that prevents hole injection from the base layer into the ballast layer. Thus, the hole injection from the base layer into the emitter layer is prevented. Accordingly, it is able to prevent the conductivity modulation of the ballast layer that is the cause of a deterioration in temperature characteristics.

Abstract: Provided is a manufacturing method of a semiconductor device, which comprises exposing a surface of a semiconductor substrate on which a heterocrystalline layer is to be grown inside of a second emitter opening portion of a hetero-junction bipolar transistor, removing water by preheat treatment in a reducing gas atmosphere, subjecting the substrate to second heat treatment in a reducing gas atmosphere at a temperature which is higher than the preheating treatment but does not adversely affect the impurity concentration distribution of another element on the semiconductor substrate, thereby removing an oxide film formed on the surface on which the heterocrystalline layer is to be grown, and then selectively causing epitaxial growth of the heterocrystalline layer on the thus cleaned surface in the second emitter opening portion. According to the present invention, reliability of a semiconductor device having a hetero-junction bipolar transistor can be improved.

Abstract: The present invention achieves the enhancement of a manufacturing yield factor and the reduction of manufacturing cost in a manufacturing method of a semiconductor device having a hetero junction bipolar transistor (HBT), a Schottky diode and a resistance element. The present invention is directed to the manufacturing method of a semiconductor device in which respective semiconductor layers which become a sub collector layer, a collector layer, a base layer, a wide gap emitter layer and an emitter layer are sequentially formed over one surface of a semiconductor substrate and, thereafter, respective semiconductor layers are processed to form the hetero junction bipolar transistor, the Schottky diode and the resistance element in a monolithic manner. An emitter electrode of the hetero junction bipolar transistor, a Schottky electrode of the Schottky diode and a resistance film of the resistance element are simultaneously formed using a same material (for example, WSiN).

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a concentration of germanium, where the concentration of germanium decreases between a first depth and a second depth in the base. According to this exemplary embodiment, the base of the heterojunction bipolar transistor further comprises a concentration of a diffusion suppressant of a base dopant, where the concentration of the diffusion suppressant decreases between a third depth and a fourth depth so as to counteract a decrease in band gap in the base between the first depth and the second depth. For example, the diffusion suppressant can be carbon and the base dopant can be boron. For example, the concentration of diffusion suppressant may decrease between the third depth and fourth depth so as to counteract the decrease in band gap at approximately the second depth.

Abstract: A method is provided for etching quaternary interface layers of InxGa1−xAsyP1−y which are formed between layers of GaAs and InGaP in heterojunction bipolar transistors (HBTs). In accordance with the method, the interface is exposed by etching the GaAs layer with an etchant that is selective to InGaP. The interface is then etched with a dilute aqueous solution of HCl and H2O2 that is selective to InGaP. The controlled etching provided by this methodology allows HBTs to be manufactured with more sophisticated, near ideal designs which may contain multiple GaAs/InGaP interfaces.

Abstract: A method for improving the SiGe bipolar yield as well as fabricating a SiGe heterojunction bipolar transistor is provided. The inventive method includes ion-implanting carbon, C, into at one of the following regions of the device: the collector region, the sub-collector region, the extrinsic base regions, and the collector-base junction region. In a preferred embodiment each of the aforesaid regions include C implants.

Abstract: A method of fabricating a feature on a substrate is disclosed. In a described embodiment the feature is the gate electrode of an MOS transistor. In this embodiment a polysilicon layer is formed on the substrate. Next, an edge definition layer of silicon nitride is formed on the feature layer. Then, a patterned edge definition layer of silicon dioxide is formed on the first edge definition layer. Then, a silicon nitride spacer is formed adjacent to an edge of the patterned second edge definition layer. Finally, the polysilicon layer is etched, forming the transistor gate electrode from the polysilicon that remains under the spacer.

Abstract: A method of fabricating a SiGe heterojunction bipolar transistor (HBT) is provided which results in a SiGe HBT that has a controllable current gain and improved breakdown voltage. The SiGe HBT having these characteristics is fabricated by forming an in-situ P-doped emitter layer atop a patterned SiGe base structure. The in-situ P-doped emitter layer is a bilayer of in-situ P-doped a:Si and in-situ P-doped polysilicon. The SiGe HBT structure including the above mentioned bilayer emitter is also described herein.

Abstract: An emitter of a heterojunction bipolar transistor has a double-layer protrusion formed of a first emitter layer and a second emitter layer and protruded outside an external base region. The protrusion of 50 nm in total thickness is enough to prevent damage during formation of the protrusion by etching or during later fabricating processes. Penetration of moisture through damaged places is eliminated. A base ohmic electrode is continuously formed on the first and second emitter layers on the external base region up to the protrusion. Thus, the protrusion is reinforced so as to be further hard to damage. By ensuring a large area for the base ohmic electrode, an alignment margin can be taken during formation of a base lead electrode.

Abstract: A method for fabricating bipolar transistor having insitu-formed epitaxial base is disclosed herein, the method including the following steps. The first step of the key feature according to one preferred embodiment of the present invention is to use a first epitaxial process to selectively grow an epitaxial collector layer in the etched first oxide layer. The first oxide layer is formed on a buried layer, which is formed on the silicon substrate. Then utilize a second epitaxial process to subsequently grow a first epitaxial-base layer and a second epitaxial-base layer. Particularly the second epitaxial process and the first epitaxial process are performed insitu. Then a patterned oxide layer and poly silicon layer are formed on the second epitaxial-base layer. Followed by etching the poly silicon layer and the patterned oxide layer, the second epitaxial-base layer is implanted, which together with the first epitaxial-base layer are etched.

Abstract: One embodiment is a method for fabricating the base of a bipolar transistor where the method comprises placing a first wafer in an undoped epi chamber. Next a first undoped base layer is grown over the first wafer. After growing the first undoped base layer, the first wafer is transferred from the undoped epi chamber into a separate doped epi chamber. A first doped base layer is then grown over the first undoped based layer in the doped epi chamber. While the first wafer is being processed in the doped epi chamber, a second wafer can be processed in the undoped epi chamber. Another embodiment is a structure produced by the disclosed method and yet another embodiment comprises a transfer chamber, a transfer arm, a bake chamber, and a separate undoped epi chamber and a doped epi chamber for practicing the disclosed method.

Abstract: A method of fabricating a bipolar transistor structure is provided in which a blanket silicon-germanium (SiGe) film is used in a self-aligned manner to form the active base region of the bipolar device, thereby eliminating the need for a complicated selective SiGe process.

Abstract: A method and structure for a bipolar transistor with a semiconductor substrate having a surface and a shallow trench isolation (STI) in the surface. The STI has an edge, a crevice region in the STI adjacent the STI edge, a base region above the STI, a silicide above the base region, an emitter structure on the surface adjacent the base region, and a crevice cover between the emitter structure and the silicide. The crevice cover maintains spacing between the emitter structure and the silicide.

Abstract: A method of manufacturing a semiconductor device comprising the step of epitaxially growing of an n-type doped layer of a semiconductor material using an n-type dopant gas, the growth process being performed at a pressure higher than 2.66×104 Pa.

Abstract: According to the disclosed method, the surface of a semiconductor wafer is covered by a protective oxide. The semiconductor wafer is then placed in a CVD reactor at a first temperature. Contaminants and the protective oxide are then removed from the surface of the semiconductor wafer at the first temperature. While contaminants and the protective oxide are being removed by the action of HCl and DCS, any silicon being removed from the surface of the silicon wafer, is being replenished so that there is no net change in the amount of silicon on the surface of the water. After removal of the contaminants and the protective oxide, epitaxial growth is performed on the surface of the semiconductor wafer at the first temperature. A structure comprising an epitaxially grown region can be fabricated according to the disclosed method.

Abstract: A bipolar transistor device with a large current capacity is formed by connecting a plurality of transistor elements to each other in parallel, each transistor element having a collector layer, a base layer, and an emitter layer formed respectively in a semiconductor substrate. In the bipolar transistor device, the base layers of a plurality of the transistor elements are extended in parallel to each other and those base layers are separated from each other. In each separated base layer, a first base electrode is formed on a part of the base layer which is separated from an emitter junction with the emitter layer, and a second base electrode is formed on another portion of the base layer closer to the emitter junction than the first base electrode. To dispose the base electrodes of a plurality of the transistor elements in parallel to each other, a base wiring is connected to the first base electrodes of those elements electrically.

Abstract: High-speed, low capacitance heterojunction bipolar transistors (HBTs) and a method for their fabrication are disclosed. The devices are fabricated by a manufacturable process which moves patterning and deposition of the base post up versus the current manufacturing process, thus permitting fabrication of a smaller base post and base metal contact and reducing the base-collector capacitance.

Abstract: A method of producing a bipolar transistor includes the step of providing a sacrificial mesa over a layer of SiGe in order to prevent a polysilicon covering layer from forming over a predetermined region of the SiGe layer forming the transistor base. After an etching process removes the sacrificial mesa and the SiGe layer is exposed, an oppositely doped material is applied over top of the SiGe layer to form an emitter. This makes it possible to realize a thin layer of silicon germanium to serve as the transistor base. This method prevents the base layer SiGe from being affected, as it otherwise would be using a conventional double-poly process.

Abstract: The present invention silicon germanium bipolar device is fabricated by growing a silicon germanium layer on a semiconductor substrate followed by depositing a first oxide layer, a first polysilicon layer, and a first nitride layer on the silicon germanium layer. A well is etched through the first nitride layer and first polysilicon layer, exposing the first oxide layer on the bottom of the well, and the first nitride layer and first polysilicon layer on the side walls of the well. To cover the exposed edges of the first nitride layer and first polysilicon layer along the walls of the well, a second nitride layer is deposited and etched, forming nitride spacers along the sides of the well. The first oxide layer at the bottom of the well area is etched, creating gaps between the silicon germanium and first polysilicon layer. A second polysilicon layer is deposited in the gaps, creating a contact region electrically connecting the first polysilicon layer to the silicon germanium layer.

Abstract: A III-N compound semiconductor bipolar transistor structure and method of manufacture. An epitaxial layer structure is formed over a substrate. The epitaxial layer structure includes a nucleation layer, a buffer layer, an emitter layer containing first type dopants (conductive type) and a base layer containing second type dopants (conductive type). Ion implantation is conducted to form a first conductive region within the base layer for forming a collector terminal. A portion of the emitter layer is etched for forming an emitter terminal. In addition, two ion-implantation regions may form inside the base layer. The ion-implantation regions serve separately as the collector terminal and the emitter terminal of the bipolar transistor, respectively, so that a more planar transistor structure is formed.

Abstract: When InP DHBTs are located in parallel to a crystallographical direction of <011>, there are several advantages in the aspect of device property such as reliability. But, in case of a direction parallel to a general <011>, there exists the limitation in reducing base-collector parasitic capacitance only by collector over-etching technique due to poor lateral-etching characteristic of the InP collector.

Abstract: A method of producing a bipolar transistor includes the step of providing a sacrificial mesa over a layer of SiGe in order to prevent a polysilicon covering layer from forming over a predetermined region of the SiGe layer forming the transistor base. After an etching process removes the sacrificial mesa and the SiGe layer is exposed, an oppositely doped material is applied over top of the SiGe layer to form an emitter. This makes it possible to realize a thin layer of silicon germanium to serve as the transistor base. This method prevents the base layer SiGe from being affected, as it otherwise would be using a conventional double-poly process.

Abstract: A method for improving the SiGe bipolar yield as well as fabricating a SiGe heterojunction bipolar transistor is provided. The inventive method includes ion-implanting carbon, C, into at one of the following regions of the device: the collector region, the sub-collector region, the extrinsic base regions, and the collector-base junction region. In a preferred embodiment each of the aforesaid regions include C implants.

Abstract: A heterojunction bipolar transistor comprising a collector layer of a first conductivity type, a base layer of a second conductivity type, and an emitter layer of the first conductivity type, which are formed on a semiconductor substrate in this order, and further a collector electrode directly or indirectly connected to the collector layer, a base electrode directly or indirectly connected to the base layer, and an emitter electrode directly or indirectly connected to the emitter layer, wherein a semiconductor protecting layer is formed on the base layer and extended outside an edge of the base layer, the base electrode is formed on the semiconductor protecting layer, and at least a region under the semiconductor protecting layer is filled with an organic insulator.

Abstract: A Heterojunction Bipolar Transistor (HBT) is provided where the SiGe base region is formed through selective deposition, after the formation of the base electrode layer and the emitter window. A sacrificial oxide layer is deposited between the collector and base electrode. The contact to the SiGe base is made at an extrinsic area, underneath the base electrode, after removal of the sacrificial oxide. The SiGe is covered with a temporary oxide layer during further processes, and this protective layer is removed immediately before the deposition of the emitter material. The selective deposition of the SiGe at a relatively late stage of the fabrication process helps insure that the film remains free of the stresses which can degrade electron mobility. A process of fabricating the above-described HBT device is also provided.

Abstract: The present invention relates to a hetero-bipolar transistor. This transistor comprises a semi-insulating InP substrate, a buffer layer on the substrate, a sub-collector layer on the buffer layer, a collector layer on the sub-collector layer, a base layer on the collector layer, a wide-gap emitter layer on the base layer and a emitter contact layer on the emitter layer. The emitter layer extends the emitter contact layer, so the edge of the emitter layer is apart from the emitter contact layer and entirely covers the region where the collector layer and the sub-collector layer are overlapped to each other. According to this configuration, the transistor shows the enhanced reliability and the improved high frequency performance.

Abstract: To provide a super high-speed heterojunction bipolar transistor, a semiconductor device including such a heterojunction bipolar transistor has a structure wherein a subcollector layer, collector layer, base layer, emitter layer (InGaP layer) and emitter cap layer are successively formed in predetermined shapes a surface of a semi-insulating GaAs substrate, an inner edge part of a base electrode overlaps a periphery of the emitter layer, and the base electrode is electrically connected to the base layer by an alloy layer formed by alloying the emitter layer under the base electrode. The emitter layer is selectively formed on the base layer. The base electrode extends from the peripheral part of the emitter layer across the base layer, and the alloy layer extends to a midway depth of the base layer. The edge of the base layer is situated further inside than the outer edge of the base electrode.

Abstract: A silicon-on-insulator substrate and its method of formation are disclosed. In another embodiment, a method for forming a high-k gate dielectric is disclosed. The silicon-on-insulator substrate is prepared by forming a lattice matched dielectric layer (20) over a semiconductor substrate (10). A thermodynamically stable dielectric layer (22) is then formed over the lattice matched dielectric layer (20). A semiconductor layer (30) is then formed over the thermodynamically stable dielectric layer (22). Formation of the high-k gate dielectric includes the processing steps used to form the silicon-on-insulator substrate and additionally includes bonding a second semiconductor substrate (50) to the semiconductor layer (30). The first semiconductor substrate (10) is then removed to expose the lattice matched dielectric layer (20). This results in a silicon substrate that has a layer of high-k dielectric material that can be used as the gate dielectric for integrated circuits formed on the substrate.

Abstract: A differential negative resistance element includes a heavily doped GaAs layer interposed between a collector layer of lightly doped GaAs and an emitter layer of heavily doped AlGaAs, is shared between a base region between the collector layer and the emitter layer, a base contact region and a channel region between the base region and the base contact region, and a depletion layer is developed into the channel region together with the collector voltage so as to exhibit a differential negative resistance characteristics, wherein the channel region is formed through an epitaxial growth and etching so that the manufacturer easily imparts target differential negative resistance characteristics to the channel region.

Abstract: An emitter of a heterojunction bipolar transistor has a double-layer protrusion formed of a first emitter layer and a second emitter layer and protruded outside an external base region. The protrusion of 50 nm in total thickness is enough to prevent damage during formation of the protrusion by etching or during later fabricating processes. Penetration of moisture through damaged places is eliminated. A base ohmic electrode is continuously formed on the first and second emitter layers on the external base region up to the protrusion. Thus, the protrusion is reinforced so as to be further hard to damage. By ensuring a large area for the base ohmic electrode, an alignment margin can be taken during formation of a base lead electrode.

Abstract: A heterojunction bipolar transistor is provided that has a reduced turn-on voltage threshold. A base spacer layer is provided and alternately an emitter layer is provided that has a lowered energy gap. The lowered energy gap of the base spacer or the emitter spacer allow the heterojunction bipolar transistor to realize a lower 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.

Abstract: Bipolar junction transistor (BJT) devices, particularly heterojunction bipolar transistor (HBT) devices, and methods of making same are described. A combination of InPSb and p-type InAs is used to create extremely high speed bipolar devices which, due to reduced turn-on voltages, lend themselves to circuits having drastically reduced power dissipation. The described HBTs are fabricated on InAs or GaSb substrates, and include an InPSb emitter. The base includes In and As, in the form of InAs when on an InAs substrate, and as InAsSb when on a GaSb substrate. The collector may be the same as the base to form a single heterojunction bipolar transistor (SHBT) or may be the same as the emitter to form a double heterojunction bipolar transistor (DHBT). Heterojunctions preferably include a grading layer, which may be implemented by continuously changing the bulk material composition, or by forming a chirped superlattice of alternating materials.

Abstract: According to a method for manufacturing a semiconductor device having a junction boundary where SiGe of a first conductivity type and Si or SiGe of a second conductivity type come in contact with each other, a portion where the junction boundary is exposed on the surface is cleaned with a first solution containing hydrofluoric acid and is then cleaned with a second solution containing sulfuric acid.

Abstract: The semiconductor device comprises a first semiconductor layer 14 formed on a semiconductor substrate 10; an outgoing base electrode 26 formed on the first semiconductor layer 14; a base layer 32 formed on the first semiconductor layer, connected to the outgoing base electrode at a side surface of the outgoing base electrode, and formed of silicon germanium containing carbon; and a second semiconductor layer 36 formed on the base layer. The base layer 32 of silicon germanium contains carbon, which prevents the action of interstitial silicon atoms, which are very influential to diffusion of boron. As a result, when the emitter layer 36, etc. are subjected to heat processing at, e.g., about 950° C., the diffusion of boron out of the base layer 32 can be prevented.

Abstract: A heterojunction bipolar transistor includes an emitter or collector region of doped silicon, a base region including silicon-germanium, and a spacer. The emitter or collector region form a heterojunction with the base region. The spacer is positioned to electrically insulate the emitter or collector region from an external region. The spacer includes a silicon dioxide layer physically interposed between the emitter or collector region and the remainder of the spacer.

Abstract: A bipolar transistor device having first and second semiconductor layers each formed on a substrate and composed of a Group III-V compound semiconductor of a first conductivity type and a third semiconductor layer formed between the first and second semiconductor layers and composed of a group IV semiconductor of a second conductivity type.

Abstract: A semiconductor device is provided with a plurality of hetero junction bipolar transistors arranged in a specified direction. Also, the semiconductor device comprises emitter wiring connected to each emitter of the plural hetero junction bipolar transistors, collector wiring connected to each collector of said plural hetero junction bipolar transistors, and base wiring connected to at least one base of said plural hetero junction bipolar transistors. Bases that are not connected to the base wiring among the bases of the plural hetero junction bipolar transistors are connected to the emitter wiring.

Abstract: According to a disclosed embodiment, a base region is grown on a transistor region. A dielectric layer is next deposited over the base region. The dielectric layer can comprise, for example, silicon dioxide, silicon nitride, or a suitable low-k dielectric. Subsequently, an opening is fabricated in the dielectric layer, and an emitter layer is formed on top of the dielectric layer and in the opening. Thereafter, an anisotropic polymerizing etch chemistry is utilized to etch the emitter layer down to a first depth, forming an emitter region in the opening. Next, a non-polymerizing etch chemistry having isotropic components is used to create a notch in the dielectric layer below the emitter region. The formation of the notch reduces the overlap area of a capacitor that forms between the emitter region and the base region, which translates to a lower level of emitter to base capacitance.

Abstract: In the method for fabricating a semiconductor device of the present invention, a collector layer of a first conductivity type is formed in a region of a semiconductor substrate sandwiched by device isolation. A collector opening is formed through a first insulating layer deposited on the semiconductor substrate so that the range of the collector opening covers the collector layer and part of the device isolation. A semiconductor layer of a second conductivity type as an external base is formed on a portion of the semiconductor substrate located inside the collector opening, while junction leak prevention layers of the same conductivity type as the external base are formed in the semiconductor substrate. Thus, the active region is narrower than the collector opening reducing the transistor area, while minimizing junction leak.

Abstract: A method for making a non-self-aligned, heterojunction bipolar transistor includes forming extrinsic base regions with a PFET source/drain implant aligned with the polysilicon in an emitter stack but which are not directly aligned with an emitter opening defined in that stack. This is achieved by making the emitter pedestal wider than the emitter opening. This advantageously removes the dependency of alignment between the extrinsic base regions and the emitter opening, thereby resulting in fewer process steps, reduced thermal cycles, and improved speed.

Abstract: The invention concerns a bipolar transistor with upper heterojunction comprising in particular stacked on a substrate: an emitter layer (EM); a base layer (BA), a collector layer (CO). In said transistor, the base-emitter junction surface is of smaller dimension than the base-collector junction surface and the material of the base layer has a lower electric conducting sensitivity to ion implantation than the electric conducting sensitivity of the material of the emitter layer to the same ion implant.

Abstract: Bipolar junction transistor (BJT) devices, particularly heterojunction bipolar transistor (HBT) devices, and methods of making same are described. A combination of InPSb and p-type InAs is used to create extremely high speed bipolar devices which, due to reduced turn-on voltages, lend themselves to circuits having drastically reduced power dissipation. The described HBTs are fabricated on InAs or GaSb substrates, and include an InPSb emitter. The base includes In and As, in the form of InAs when on an InAs substrate, and as InAsSb when on a GaSb substrate. The collector may be the same as the base to form a single heterojunction bipolar transistor (SHBT) or may be the same as the emitter to form a double heterojunction bipolar transistor (DHBT). Heterojunctions preferably include a grading layer, which may be implemented by continuously changing the bulk material composition, or by forming a chirped superlattice of alternating materials.

Abstract: Disclosed is a manufacturing method to fabricate Heterojunction Bipolar Transistors (HBTs) that enables self-alignment of emitter and base metal contact layers with precise sub-micron spacing using a dielectric-assisted metal lift-off process. Such an HBT process relies on the formation of an “H-shaped” dielectric (i.e., Si3N4/SiO2) mask conformally deposited on top of the emitter contact metalization that is used to remove excess base metal through lift-off by a wet chemical HF-based etch. This HBT process also uses a thin selective etch-stop layer buried within the emitter layer to prevent wet chemical over-etching to the base and improves HBT reliability by forming a non-conducting, depleted ledge above the extrinsic base layer. The geometry of the self-aligned emitter and base metal contacts in the HBT insures conformal coverage of dielectric encapsulation films, preferably Si3N4 and/or SiO2, for reliable HBT emitter p-n junction passivation.

Abstract: A heterojunction bipolar transistor (HBT) (20) with alternating layers of gallium nitride (GaN) and aluminum gallium nitride (AlGaN) with varying Al composition forming a graded superlattice structure in the base layer (28) includes. The thin layers of AlGaN in the base layer (28) increases the base p-type carrier concentration. Grading of the Al composition in the thin AlGaN layers induces an electrostatic field across the base layer (28) that increases the carrier velocity and reduces the carrier transit time. The structure thus decreases the transit time and at the same time increases the p-type carrier concentration to improve the operating efficiency of the device.

Abstract: A heterojunction bipolar transistor (HBT) having an emitter structure capable of reducing the current crowding effect and preventing thermal instabilities is disclosed, wherein a negative differential resistance. (NDR) element is added to the layer structure of the conventional emitter. In accordance with the invention, the NDR element can be implemented, for example, by a Resonant Tunnel Diode (RTD) or an Esaki Diode structure. The NDR element is designed to limit the tunneling current to the maximal emitter current density required for safe transistor operation, thereby also reducing the current crowding effect.