GaN HEMT Buffer Layer Lattice Mismatch Mitigation
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Solution Overview
Problem
Lattice mismatch between silicon and gallium nitride (GaN) materials poses a significant challenge in semiconductor devices, leading to lattice dislocation and reduced performance in high electron mobility transistor (HEMT) devices.
Innovation Solution
Incorporating a group III-V-VI semiconductor compound layer between the silicon substrate and the GaN layer to act as a buffer and reduce lattice dislocation, with a nucleation layer to further mitigate differences in lattice constants and thermal expansion coefficients, thereby improving the mobility of two-dimensional electron gas (2DEG).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a GaN layer is directly formed on a silicon substrate, then the device can be manufactured with simpler process, but lattice mismatch causes lattice dislocation and reduced device performance
Solution Approach 1:
A group III-V-VI semiconductor compound layer is introduced as an intermediary buffer layer between the silicon substrate and the GaN layer. This intermediate layer has a lattice constant that is between that of silicon and GaN, effectively bridging the lattice mismatch and reducing dislocation density, thereby improving device performance while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses composite material structures including the group III-V-VI semiconductor compound layer combined with GaN layer on silicon substrate. This composite structure leverages the properties of each material to achieve both lattice matching and high electron mobility, resolving the contradiction between manufacturing simplicity and device performance
2Reliability
If buffer layers are added to reduce lattice mismatch, then device performance is improved, but the device structure becomes more complex
Solution Approach 1:
The buffer structure is segmented into multiple functional layers: a nucleation layer for initial crystal growth, and a group III-V-VI semiconductor compound buffer layer for lattice matching. This segmentation allows each layer to perform its specific function efficiently, improving performance while managing structural complexity through functional division
Data Source
AI summary
Provided is a semiconductor structure including a substrate, a first semiconductor layer, a second semiconductor layer, a gate electrode, a source electrode and a drain electrode. The first semiconductor layer contains a group III-V-VI semiconductor compound layer and is disposed on the substrate. The second semiconductor layer includes a group III-V semiconductor compound and is disposed on the first semiconductor layer. The gate electrode is disposed on the second semiconductor layer. The source electrode and the drain electrode are disposed on the second semiconductor layer beside the gate electrode.