A semiconductor-based stress sensor can include a bipolar transistor device with first and second collector terminals. An excitation circuit can provide an excitation signal to an emitter terminal of the bipolar transistor device, and a physical stress indicator for the semiconductor can be provided based on a relationship between signals measured at the collector terminals in response to the excitation signal. The signals can indicate a charge carrier mobility characteristic of the semiconductor, which can be used to provide an indication of physical stress. In an example, the physical stress indicator is based on a current deflection characteristic of a base region of the transistor device.

Bi-directional trench power switches. At least one example is a semiconductor device comprising: an upper base region associated with a first side of a substrate of semiconductor material; an upper-CE trench defined on the first side, the upper-CE trench defines a proximal opening at the first side and a distal end within the substrate; an upper collector-emitter region disposed at the distal end of the upper-CE trench; a lower base region associated with a second side of substrate; and a lower collector-emitter region associated with the second side.

Memory systems and devices with source plate discharge circuits (and associated methods) are described herein. In one embodiment, a memory device includes (a) a plurality of memory cells, (b) a source plate electrically coupled to the plurality of memory cells, and (c) a discharge circuit. The discharge circuit can include a bipolar junction transistor device electrically coupled to the source plate and configured to drop a voltage at the source plate by, for example, discharging current through the bipolar junction transistor device. In some embodiments, the bipolar junction transistor device can be activated using a low-voltage switch or a high-voltage switch electrically coupled to the bipolar junction transistor. In these and other embodiments, the bipolar junction transistor device can operate in an avalanche mode while discharging current to drop the voltage at the source plate.

In a semiconductor device, a semiconductor substrate has an IGBT region and a FWD, and includes a first conductivity type drift layer, a second conductivity type base layer disposed on the drift layer, a second conductivity type collector layer disposed opposite to the base layer with respect to the drift layer in the IGBT region, and a first conductivity type cathode layer disposed opposite to the base layer with respect to the drift layer in the FWD region. The collector layer includes an extension portion that covers only a part of the cathode layer on a side adjacent to the drift layer. Alternatively, the collector layer includes an extension portion that entirely covers a region of the cathode layer adjacent to the drift layer, and has an area density of 3.5×10.sup.12 cm.sup.−2 or less.

A vertical high-blocking III-V bipolar transistor, which includes an emitter, a base and a collector. The emitter has a highly doped emitter semiconductor contact region of a first conductivity type and a first lattice constant. The base has a low-doped base semiconductor region of a second conductivity type and the first lattice constant. The collector has a layered low-doped collector semiconductor region of the first conductivity type with a layer thickness greater than 10 μm and the first lattice constant. The collector has a layered highly doped collector semiconductor contact region of the first conductivity type. A first metallic connecting contact layer is formed in regions being integrally connected to the emitter. A second metallic connecting contact layer is formed in regions being integrally connected to the base. A third metallic connecting contact region is formed at least in regions being arranged beneath the collector.

In one example, a sensor includes a heterojunction bipolar transistor and component sensing surface coupled to the heterojunction bipolar transistor via an extended base component. In another example, a biosensor for detecting a target analyte includes a heterojunction bipolar transistor and a sensing surface. The heterojunction bipolar transistor includes a semiconductor emitter including an emitter electrode for connecting to an emitter voltage, a semiconductor collector including a collector electrode for connecting to a collector voltage, and a semiconductor base positioned between the semiconductor emitter and the semiconductor collector. The sensing surface is coupled to the semiconductor base of the heterojunction bipolar transistor via an extended base component and includes a conducting film and a reference electrode.

Methods of maintaining a state of a memory cell without interrupting access to the memory cell are provided, including applying a back bias to the cell to offset charge leakage out of a floating body of the cell, wherein a charge level of the floating body indicates a state of the memory cell; and accessing the cell.

This disclosure relates to methods for forming bipolar transistors, such as heterojunction bipolar transistors, having at least one grading in the collector. In some embodiments, the methods include forming a sub-collector. In some embodiments the methods include forming a primary collector region with at least one grading having a doping concentration that decreases away from the sub-collector. In some embodiments the methods further include forming a secondary collector region to abut a base of the bipolar transistor and having a doping concentration of at least about 3×10.sup.16 cm.sup.−3 at an interface with the base. Such bipolar transistors can be implemented, for example, in power amplifiers.

Structures for a bipolar junction transistor and methods of forming a structure for a bipolar junction transistor. The structure includes an emitter having a raised portion, a collector having a raised portion, and a base having a base layer and an extrinsic base layer stacked with the base layer. The base layer and the extrinsic base layer are positioned in a lateral direction between the raised portion of the emitter and the raised portion of the collector, the base layer has a first width in the lateral direction, the extrinsic base layer has a second width in the lateral direction, and the second width is greater than the first width.

Various embodiments of the present disclosure are directed towards a method for forming a bipolar junction transistor (BJT). A dielectric film is deposited over a substrate and comprises a lower dielectric layer, an upper dielectric layer, and an intermediate dielectric layer between the lower and upper dielectric layers. A first semiconductor layer is deposited over the dielectric film and is subsequently patterned to form an opening exposing the dielectric film. A first etch is performed into the upper dielectric layer through the opening to extend the opening to the intermediate dielectric layer. Further, the first etch stops on the intermediate dielectric layer and laterally undercuts the first semiconductor layer. Additional etches are performed to extend the opening to the substrate. A lower base structure and an emitter are formed stacked in and filling the opening, and the first semiconductor layer is patterned to form an upper base structure.