AlGaN Interlayer Structure for III-N Transistor Etch and Mobility Balance
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Solution Overview
Problem
There is a need for improved III-N material based transistors, particularly for high voltage and high frequency applications, where existing devices face challenges in etch reliability, threshold voltage uniformity, and electron mobility due to alloy scattering and gate leakage issues.
Innovation Solution
The implementation of a low aluminum concentration aluminum gallium nitride interlayer in III-N devices, which acts as an etch stop layer and gate liner, reduces alloy scattering, improves etch reliability, and decreases gate leakage, thereby enhancing electron mobility and threshold voltage uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high aluminum concentration aluminum gallium nitride layer is used, then the etch selectivity and gate liner function are improved, but alloy scattering increases and electron mobility decreases
Solution Approach 1:
The patent divides the aluminum gallium nitride layer into two distinct layers: a first layer with low aluminum concentration (0.05-0.15) and a second layer with high aluminum concentration (0.25-0.40). This segmentation allows each layer to perform its optimal function - the low aluminum layer provides high electron mobility and uniform threshold voltage, while the high aluminum layer provides etch selectivity and gate liner functionality.
Solution Approach 2:
Different regions of the aluminum gallium nitride structure are assigned different aluminum concentrations based on their specific functional requirements. The low aluminum concentration region is positioned where electron transport is critical (near the GaN channel), while the high aluminum concentration region is positioned where etch resistance is critical (near the gate electrode interface).
2Reliability
If a high aluminum concentration aluminum gallium nitride layer is used, then the gate liner function is improved, but gate leakage increases
Solution Approach 1:
The low aluminum concentration layer acts as an intermediary between the GaN channel and the high aluminum concentration layer. It provides a transition region that prevents direct contact between the gate electrode and the high aluminum region, thereby reducing gate leakage while still allowing the high aluminum layer to provide gate liner protection.
Solution Approach 2:
The patent creates a composite structure combining two aluminum gallium nitride layers with different aluminum concentrations. This composite material approach allows the structure to simultaneously exhibit properties of both low aluminum (high mobility, low leakage) and high aluminum (high etch resistance, good gate liner) regions.
3Ease of manufacture
If aluminum gallium nitride layers are used, then the device structure is formed, but alloy scattering occurs and electron mobility is reduced
Solution Approach 1:
The patent optimizes the aluminum concentration parameter in the first layer to a low range (0.05-0.15), which minimizes alloy scattering and maximizes electron mobility. This parameter optimization allows the device to achieve high electron mobility while still forming a complete functional structure with the additional high aluminum concentration layer.
Data Source
AI summary
Devices, transistor structures, systems, and techniques are described herein related to low aluminum concentration aluminum gallium nitride interlayers for group III-nitride enhancement mode transistors. The low aluminum concentration aluminum gallium nitride interlayer includes a lower aluminum concentration than a polarization layer of the transistor, such that the polarization layer induces a two-dimensional electron gas in a semiconductor layer of the transistor. The low aluminum concentration aluminum gallium nitride interlayer may be implemented as an etch stop layer, as a gate liner, or both.