Structures for a heterojunction bipolar transistor and methods of forming a structure for a heterojunction bipolar transistor. The structure comprises a first semiconductor layer including a first portion, a second portion, and a third portion between the first portion and the second portion, a first terminal including a first semiconductor region on the first portion of the first semiconductor layer, a second terminal including a second semiconductor region on the second portion of the first semiconductor layer, an intrinsic base laterally disposed between the first terminal and the second terminal, and an extrinsic base on the intrinsic base. The intrinsic base includes a doped region in the third portion of the first semiconductor layer, and the doped region has a dopant depth profile with a dopant concentration that is asymmetrical relative to the first terminal and the second terminal.

Embodiments of the disclosure provide a crystalline semiconductor layer between a bipolar transistor structure and a field effect transistor (FET) structure. The structure includes a dielectric layer on a back-gate semiconductor layer, a bipolar transistor structure on the dielectric layer, FET structure on the dielectric layer, and a crystalline semiconductor layer on the dielectric layer between the bipolar transistor structure and the FET structure. The crystalline semiconductor layer includes a terminal of the bipolar transistor structure and a terminal of the FET structure.

A heterojunction bipolar transistor device includes a substrate, a metallic sub-collector layer, a collector layer, a base layer, an emitter layer, a base electrode, and a plurality of emitter strips. The metallic sub-collector layer is formed over the substrate. The collector layer is formed over the metallic sub-collector layer. The base layer is formed over the collector layer. The emitter layer is formed over the base layer. The base electrode is formed over the base layer and includes a plurality of base fingers. The plurality of emitter strips are formed over the emitter layer and are arranged alternately with the plurality of base fingers.

In some embodiments, a method for forming a semiconductor structure includes forming an isolation structure in a collector semiconductor layer, forming a base dielectric layer over the collector semiconductor layer, and forming a first recess in the base dielectric layer. A base contact layer is formed over the base dielectric layer and in the first recess. A dielectric layer is formed over the base contact layer. A second recess is formed in the dielectric layer and the base contact layer to expose the collector semiconductor layer. Portions of the base contact layer are removed to form undercut regions under the base contact layer and over the collector semiconductor layer. A base semiconductor layer is formed in the second recess and the undercut regions. The base semiconductor layer contacts the base contact layer and the collector semiconductor layer. An emitter semiconductor layer is formed in the second recess and over the base semiconductor layer.

The present disclosure generally relates to semiconductor processing for a bipolar junction transistor (BJT). In an example, a semiconductor device includes a semiconductor substrate and a bipolar junction transistor on the semiconductor substrate. The bipolar junction transistor includes a collector layer on the semiconductor substrate, a base layer on the collector layer, a raised base layer on the base layer, a dielectric spacer on the base layer and along a sidewall of the raised base layer, and an emitter layer on the base layer. The dielectric spacer is laterally between the raised base layer and the emitter layer. The emitter layer extends over the dielectric spacer and at least partially over the raised base layer. The raised base layer has a substantially continuous upper surface from a distance away from the emitter layer to the dielectric spacer underlying the emitter layer.

A compound transistor comprises a first transistor structure and a second transistor structure. The first transistor structure includes a collector layer, a base layer on the collector layer, an emitter layer on a first portion of the base layer, and a base metal contact on a second portion of the base layer. The second transistor structure includes a channel layer directly on a first portion of the emitter layer and a barrier layer on the channel layer. A plurality of electrodes including a source, a gate, and a drain are formed on the barrier layer such that the source is electrically coupled to the base metal contact.

A display device may include: a base layer including a display area and a non-display area; and a plurality of pixels provided on the display area, and each including a plurality of sub-pixels. Each of the sub-pixels may include a pixel circuit layer, and a display element layer including an emission area formed to emit light, and a non-emission area provided around a perimeter of the emission area. The display element layer may include: a partition wall provided on the emission area of each of the sub-pixels; a bank provided on the non-emission area of each sub-pixel, and disposed on a surface equal to a surface on which the partition wall is disposed; a first electrode and a second electrode provided on the partition wall and spaced apart from each other; and at least one light emitting element provided between the first and second electrodes in the emission area of each sub-pixel, and configured to emit the light.

Structures including devices, such as transistors, integrated on a bulk semiconductor substrate and methods of forming a structure including devices, such as transistors, integrated on a bulk semiconductor substrate. The bulk semiconductor substrate contains a single-crystal semiconductor material having a diamond crystal lattice structure and a <111> crystal orientation. A first transistor is formed in a first device region of the bulk semiconductor substrate, and a second transistor is formed in a second device region of the bulk semiconductor substrate. The second transistor includes a layer stack on the bulk semiconductor substrate, and the layer stack includes a layer comprised of a III-V compound semiconductor material.

The disclosure provides an isolation stack for a bipolar transistor (BT), and related methods. A structure of the disclosure includes a first isolation layer on a subcollector. A first air gap is between the first isolation layer and a collector of a BT. A second isolation layer is on the first isolation layer and adjacent an intrinsic base of the BT. A third isolation layer is on the second isolation layer, vertically between the second isolation layer and an extrinsic base of the BT. A second air gap is adjacent the third isolation layer and below the extrinsic base.

Aspects disclosed in the detailed description include an impure Indium Phosphide (InP) semiconductor substrate. Related apparatus and methods are also disclosed. In this regard, in some exemplary aspects disclosed herein, a semiconductor substrate comprising a silicon layer and an impure InP layer adjacent to the silicon layer. The impure InP layer may be epitaxially grown on a Silicon (Si) nanoridge base or directly bonded to the silicon layer after being epitaxially grown and cleaved. Utilizing an impure InP layer advantageously provides structural strength to be deployed in a 300 millimeter wafer process while achieving the electrical and thermal characteristic of InP it provides in a semiconductor substrate.