GaN Device Current Collapse Control via Recessed Multilayer Stack
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Solution Overview
Problem
Gallium nitride-based semiconductor devices face current collapse issues due to deep traps, leading to increased on-resistance and decreased current during high-voltage applications, and challenges with substrate compatibility causing cracking and defects.
Innovation Solution
A gallium nitride device is formed on a semiconductor substrate with recessed regions, featuring a seed layer, optional buffer layer, and doped gallium nitride layer, with specific dimensions to minimize current collapse and mechanical stress, using metal organic chemical vapor deposition (MOCVD) to grow epitaxial layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If GaN layers are grown directly on semiconductor substrates, then device fabrication is simplified, but substrate compatibility issues cause cracking and defects
Solution Approach 1:
The patent introduces an optional buffer layer between the semiconductor substrate and the GaN layers to act as an intermediary that accommodates lattice mismatch and thermal expansion differences, preventing cracking and defects while maintaining fabrication simplicity
Solution Approach 2:
The patent segments the GaN structure into multiple layers (seed layer, buffer layer, doped GaN layer) with specific thicknesses and compositions, allowing each layer to be optimized for its specific function in managing substrate compatibility issues
2Power
If high voltage is applied to GaN devices, then device performance is enhanced, but current collapse occurs due to deep traps
Solution Approach 1:
The patent modifies the physical and chemical parameters of the GaN layers, including thickness (0.5-2.0 microns), doping concentration (1e18 to 1e19 atoms/cm³), and composition, to optimize electrical properties and reduce current collapse while maintaining high power capability
Solution Approach 2:
The patent applies different doping concentrations and layer compositions at different locations and depths within the GaN structure, with higher doping near the substrate to compensate for deep trap effects and lower doping in the channel region to maintain mobility
3Strength
If GaN layer thickness is increased, then mechanical robustness improves, but substrate bow and cracking increase
Solution Approach 1:
The patent optimizes the GaN layer thickness to a specific range (0.5-2.0 microns) that provides sufficient mechanical robustness while remaining thin enough to minimize stress accumulation and prevent substrate bow and cracking
Solution Approach 2:
The patent divides the thick GaN structure into multiple thinner layers separated by buffer layers, distributing the mechanical stress throughout the structure rather than concentrating it in a single thick layer
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 structured gallium nitride device exhibits improved current collapse response and mechanical robustness, reducing current collapse to less than 10% and minimizing substrate bow and cracking, while maintaining high electron mobility and efficiency.
Implementation Method 1
using metal organic chemical vapor deposition (MOCVD) to grow epitaxial layers
Implementation Method 2
doped gallium nitride layer
Data Source
AI summary
A GaN device is formed on a semiconductor substrate having a plurality of recessed regions formed in a surface thereof. A seed layer, optional buffer layer, and gallium nitride layer such as a carbon-doped gallium nitride layer are successively deposited within the recessed regions. Improved current collapse response of the GaN device is attributed to maximum length and width dimensions of the multilayer stack.