Transistor Structure Using Composite Si-GaAs Materials
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Solution Overview
Problem
Current semiconductor materials for transistor structures, such as Si, SiC, and GaN, face limitations in drift mobility and gate quality, hindering the performance of power transistors, particularly in achieving low on-state resistance and high drain-to-source breakdown voltage.
Innovation Solution
A transistor structure is designed with different semiconductor base materials for the source and channel regions (e.g., Si) and the drift structure (e.g., GaAs), allowing for improved carrier mobility and energy band alignment to enhance on-state and off-state device characteristics, including the use of a superjunction structure with a compensation layer to balance charge and increase breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Si is used as the semiconductor base material for the channel region, then the transistor structure is simple to manufacture, but the drift mobility is relatively low
Solution Approach 1:
The patent employs a composite semiconductor structure where the channel region is made of Si and the drift structure is made of GaAs. This composite approach allows the channel to benefit from Si's ease of manufacture while the drift structure benefits from GaAs's high drift mobility, thereby resolving the contradiction between manufacturing simplicity and speed performance.
Solution Approach 2:
The patent applies local quality by using different semiconductor materials in different regions of the transistor. Specifically, Si is used in the channel region where ease of manufacture is prioritized, while GaAs is used in the drift structure where high drift mobility is critical for performance. This regional differentiation resolves the contradiction by optimizing each region for its specific functional requirement.
2Strength
If SiC is used as the semiconductor base material, then the breakdown voltage is improved, but the inversion layer mobility is relatively low
Solution Approach 1:
The patent uses a composite structure combining Si channel with GaAs drift structure. The GaAs drift structure provides both high drift mobility (resolving the mobility issue) and adequate breakdown voltage capability, thereby resolving the contradiction between breakdown voltage and inversion layer mobility that exists in single-material SiC devices.
Solution Approach 2:
The patent changes the material parameter (semiconductor base material) from a single material system to a multi-material system. By selecting GaAs for the drift structure, the patent achieves a favorable balance between drift mobility and breakdown voltage, resolving the contradiction present in SiC-based devices.
3Speed
If GaN is used as the semiconductor base material, then the electron mobility is high, but gate quality issues arise and depletion-mode operation is required
Solution Approach 1:
The patent applies local quality by using Si for the channel region where good gate quality and enhancement-mode operation are required, while using GaAs for the drift structure where high electron mobility is needed. This regional differentiation resolves the contradiction between electron mobility and gate quality by assigning each material to the region where it performs best.
Solution Approach 2:
The composite Si-GaAs structure allows the Si channel to provide reliable gate characteristics and enhancement-mode operation, while the GaAs drift structure provides high electron mobility. This composite approach resolves the contradiction between electron mobility and gate quality that limits GaN device performance.
4Device complexity
If only Si is used as the semiconductor base material, then the device structure is simple, but the on-state resistance is high
Solution Approach 1:
The patent uses a composite Si-GaAs structure where the GaAs drift structure provides superior electrical characteristics including lower on-state resistance. While this increases device complexity compared to pure Si, the performance improvement in on-state resistance justifies the added complexity, effectively resolving the contradiction between structure simplicity and energy loss.
Solution Approach 2:
The patent changes the material composition parameter from homogeneous Si to heterogeneous Si-GaAs. This material parameter change enables the drift structure to achieve lower on-state resistance through GaAs's superior electrical properties, resolving the contradiction between structure simplicity and energy loss.
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 significantly lower on-state resistance (RDSON) and improved drain-to-source breakdown voltage, making the transistors well-suited for high-voltage applications, with RDSON reduced by an order of magnitude compared to similar transistors using only Si as the semiconductor base material.
Implementation Method 1
The carrier mobility of the drift structure is greater than the carrier mobility of the channel region
Implementation Method 2
a superjunction structure with a compensation layer to balance charge and increase breakdown voltage
Data Source
AI summary
An electronic device can include a transistor structure. In an embodiment, the transistor structure can include a channel region and a drift structure including different semiconductor base materials. In another embodiment, the transistor structure can include a source region and a drain structure including a first region, wherein the source region and the first region include different semiconductor base materials and have the same conductivity type. In another aspect, a process of forming an electronic device can include forming a semiconductor layer; forming a body region; patterning the body region and the semiconductor layer to define a trench having a sidewall; forming a first region of a drain structure along the sidewall of the trench, wherein the first region and body region include different semiconductor base materials and different conductivity types.