A bipolar junction transistor has a collector over a substrate, a base over the collector, and an emitter over the base. The base includes a III-V ternary semiconductor alloy including first, second, and third elements, and having a narrower bandgap than a binary semiconductor alloy including only the first and second elements. At least a portion of the base has a differential concentration of the third element such that a concentration of the third element at a first location in the base is greater than at a second location in the base, the second location between the first location and the collector.

A bipolar junction transistor a base over a collector, the base including a III-V ternary semiconductor alloy including first, second, and third elements. The LI-V ternary semiconductor alloy has a narrower bandgap than a binary semiconductor alloy including only the first and second elements. A ledge between an emitter and a base contact being 0.5 m or less.

A bipolar junction transistor has a collector over a substrate and a base structure over the collector, the base including a III-V ternary semiconductor alloy, the base having a base contact formed thereon. An emitter is over the base structure, and a ledge between the emitter structure and the base contact is 0.3 m or less.

A bipolar junction transistor has a collector over a substrate and a multi-layer base structure over the collector, and an emitter over the base structure. The multi-layer base structure includes a first layer having a first III-V semiconductor alloy and a second layer having a second III-V semiconductor alloy having a different composition of elements than the first III-V semiconductor alloy. The second layer has a narrower bandgap than the first layer. The first layer is positioned between the collector and the second layer.

The present invention provides a bipolar transistor, a method for forming the bipolar transistor, a method for turning on the bipolar transistor, and a band-gap reference circuit, virtual ground reference circuit and double band-gap reference circuit with the bipolar transistor. The bipolar transistor includes: a Silicon-On-Insulator wafer; a base area, an emitter area and a collector area; a base area gate dielectric layer on a top silicon layer and atop the base area; a base area control-gate on the base area gate dielectric layer; an emitter electrode connected to the emitter area via a first contact; a collector electrode connected to the collector area via a second contact; and a base area control-gate electrode connected to the base area control-gate via a third contact. Processes of forming the bipolar transistor are fully compatible with traditional standard CMOS processes; and the base current to turn on the bipolar transistor is based on the GIDL current and formed by applying a voltage to the base area control-gate electrode without any need of contact to the base.

A bipolar junction transistor includes an emitter, a base contact, a collector and a shallow trench isolation. The base contact has two base fingers that form a corner to receive the emitter. The collector has two collector fingers extending along the base fingers of the base contact. The shallow trench isolation is disposed in between the emitter and the base contact and in between the base contact and the collector.

The disclosure provides bipolar transistor structures with a cavity below an extrinsic base, and methods to form the same. A structure of the disclosure provides a bipolar transistor structure including an extrinsic base protruding from an intrinsic base of a bipolar transistor. The extrinsic base extends over a cavity. An insulator is horizontally adjacent the cavity and below a portion of the extrinsic base. A collector extension region of the bipolar transistor structure extends laterally below the insulator and the cavity.

A method of making a bipolar transistor includes: forming a first collector part of a first conductivity type in a semiconductor layer; forming a first insulating region made of a first insulating material on the first collector part; forming a conduction layer intended to form a first doped base part of the second conductivity type on the first insulating region; forming an opening having a first width in the conduction layer that emerges onto the first insulating region; forming an insulating layer on the conduction layer and in the opening; forming a cavity in the insulating layer and in the first insulating region that emerges onto a portion of the first collector part through the opening, the cavity having at the level of the opening a second width smaller than the first width; and forming a second collector part in the cavity on the portion of the first collector part.

In one aspect, a method of fabricating a bipolar transistor device on a wafer includes the following steps. A dummy gate is formed on the wafer, wherein the dummy gate is present over a portion of the wafer that serves as a base of the bipolar transistor. The wafer is doped to form emitter and collector regions on both sides of the dummy gate. A dielectric filler layer is deposited onto the wafer surrounding the dummy gate. The dummy gate is removed selective to the dielectric filler layer, thereby exposing the base. The base is recessed. The base is re-grown from an epitaxial material selected from the group consisting of: SiGe, Ge, and a III-V material. Contacts are formed to the base. Techniques for co-fabricating a bipolar transistor and CMOS FET devices are also provided.

An integrated sensor for detecting the presence of an environmental material and/or condition includes a sensing structure and first and second bipolar junction transistors (BJTs). The first BJT has a base that is electrically coupled with the sensing structure and is configured to generate an output signal indicative of a change in stored charge in the sensing structure. The second BJT is configured to amplify the output signal of the first bipolar junction transistor. The first and second BJTs and the sensing structure are monolithically formed a common substrate.