Single Column BJT with All-Around Extrinsic Base
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Solution Overview
Problem
Existing bipolar junction transistor (BJT) fabrication techniques face challenges in achieving small base-collector capacitance and symmetrical emitter/collector configurations, particularly when using III-V compound semiconductors, which are essential for high-performance and high-voltage applications.
Innovation Solution
The development of a single column bipolar junction transistor structure with a heavily doped epitaxially grown III-V compound semiconductor base layer, surrounded by a doped extrinsic base, and a top III-V compound semiconductor layer, where the base layer is located between the bottom and top semiconductor layers, allowing for a vertical column configuration and enabling the formation of a trench to create a space for the extrinsic base growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BJT fabrication techniques are used, then manufacturing process is simpler, but base-collector capacitance is larger and emitter/collector symmetry is difficult to achieve
Solution Approach 1:
The patent inverts the conventional fabrication sequence by first forming the base layer and then growing emitter and collector layers symmetrically on opposite sides. This reverse approach enables symmetrical emitter/collector configurations and reduces base-collector capacitance, as the base is fully surrounded by the extrinsic base region before final layer formation.
Solution Approach 2:
The patent transitions from planar BJT structures to vertical columnar structures grown along the <110> crystal direction. This dimensional change enables the extrinsic base to completely surround the base layer in three dimensions, creating the desired symmetrical configuration and reducing parasitic capacitances through the vertical geometry.
2Reliability
If III-V compound semiconductors are used for high-performance applications, then device performance is improved, but fabrication challenges increase due to material complexity
Solution Approach 1:
The patent utilizes specific crystal orientation parameters by growing all layers along the <110> direction, which is optimal for III-V compound semiconductors. This parameter change in growth orientation improves material quality and device performance while enabling the vertical columnar structure that simplifies the overall fabrication process despite material complexity.
Solution Approach 2:
The patent performs preliminary epitaxial growth of the base layer with controlled doping and composition before subsequent emitter and collector formation. This preliminary action establishes the foundation for high-performance operation and enables symmetric structure formation, reducing overall fabrication complexity despite using III-V materials.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in relatively small base-collector capacitance and allows for symmetrical emitter/collector configurations, facilitating the bottom-up formation of BJT devices with improved performance and voltage handling capabilities.
Implementation Method 1
The bottom semiconductor layer is heavily doped and consists essentially of an epitaxially grown III-V compound semiconductor material
Data Source
AI summary
A vertical, single column compound semiconductor bipolar junction transistor device includes an all-around extrinsic base. Homojunction and heterojunction devices are formed using III-V compound semiconductor materials with appropriate bandgaps. Fabrication of the transistor device includes epitaxially growing a III-V compound semiconductor base region on a heavily doped III-V compound semiconductor bottom layer. A polycrystalline emitter/collector layer and the all-around extrinsic base are grown on the base region.