Lateral III-V Bipolar Transistor on Silicon for High Gain
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Solution Overview
Problem
Current bipolar junction transistors (BJTs) face limitations in achieving high current gain and high-speed performance due to the use of similar semiconductor materials for the base and emitter, which restricts their application in high-voltage and high-speed applications.
Innovation Solution
A lateral bipolar junction transistor (LBJT) structure is developed using type III-V semiconductor materials for the emitter, base, and collector regions, with a buried oxide layer between the type IV semiconductor substrate and these regions, allowing for epitaxial growth and different material compositions for each region to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If similar semiconductor materials are used for base and emitter regions, then manufacturing simplicity is maintained, but current gain and high-speed performance are limited
Solution Approach 1:
The patent applies local quality by using different III-V semiconductor materials for different regions of the transistor. The emitter region uses a first III-V semiconductor material with a wider band gap, while the base region uses a second III-V semiconductor material with a narrower band gap. This material differentiation at local levels enables higher current gain and improved high-speed performance while maintaining heteroepitaxial growth compatibility on silicon substrates.
Solution Approach 2:
The patent employs composite materials by combining different III-V semiconductor materials (such as GaAs, AlGaAs, InP, InGaAs) to form the emitter and base regions. This composite structure creates a heterojunction that leverages the advantageous properties of each material - the wider band gap material provides high breakdown voltage and the narrower band gap material provides high mobility - resulting in superior transistor performance compared to single-material structures.
2Reliability
If heterojunction structure with different band gap materials is implemented, then current gain increases, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the band gap parameters of the semiconductor materials used in different regions. By selecting III-V semiconductor materials with specific band gap values (wider for emitter, narrower for base), the patent optimizes carrier injection efficiency and current gain while managing the complexity through controlled material parameter selection rather than arbitrary complexity.
Solution Approach 2:
The patent uses a buried oxide layer as an intermediary between the silicon substrate and the III-V semiconductor layers. This intermediary layer facilitates heteroepitaxial growth by providing a suitable interface that reduces lattice mismatch and dislocation propagation, thereby enabling the complex heterojunction structure to be manufactured on standard silicon substrates without requiring direct growth on mismatched substrates.
3Speed
If type III-V semiconductor materials are used for emitter and base regions, then high-speed performance and breakdown voltage improve, but compatibility with standard silicon substrate decreases
Solution Approach 1:
The patent employs a buried oxide layer as an intermediary between the silicon substrate and the III-V semiconductor layers. This intermediary facilitates heteroepitaxial growth by providing a suitable interface that reduces lattice mismatch and dislocation propagation, thereby enabling the complex heterojunction structure to be manufactured on standard silicon substrates without requiring direct growth on mismatched substrates.
Solution Approach 2:
The patent transitions from planar transistor structures to vertical heteroepitaxial structures by growing III-V semiconductor layers perpendicular to the silicon substrate surface. This dimensional change enables the integration of high-performance III-V materials with standard silicon substrates by utilizing the vertical dimension for material growth while maintaining compatibility with standard silicon fabrication processes in the lateral dimension.
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
The LBJT structure achieves higher current gain and larger breakdown voltage, enabling high-speed and high-voltage applications with improved cut-off frequency, surpassing silicon-based BJTs and CMOS counterparts.
Implementation Method 1
A first type III-V semiconductor material layer is epitaxially grown on sidewalls of the fin structure from the type IV semiconductor on insulator layer
Implementation Method 2
a buried oxide layer is present between the type IV semiconductor substrate and the emitter region, the base region and the collector region
Data Source
AI summary
A lateral bipolar junction transistor including an emitter region, base region and collector region laterally orientated over a type IV semiconductor substrate, each of the emitter region, the base region and the collector region being composed of a type III-V semiconductor material. A buried oxide layer is present between the type IV semiconductor substrate and the emitter region, the base region and the collector region. The buried oxide layer having a pedestal aligned with the base region.