GaN HEMT Barrier Layer Segmentation for Low On-Resistance
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Solution Overview
Problem
Current GaN HEMT devices face challenges in achieving improved performance specifications and reliability due to limitations in adjusting the Al component content and thickness of the AlGaN barrier layer, leading to compromised 2DEG concentration and increased on-resistance, as well as etching damage and defects.
Innovation Solution
The innovative approach involves separately forming the first and second barrier layers through primary and secondary epitaxy, allowing independent adjustment of their Al component content and thickness, with the first barrier layer having a higher Al content and thickness in the active region to enhance 2DEG concentration and the second barrier layer having a lower Al content and thickness in the gate region to stabilize the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single AlGaN barrier layer is used with fixed Al content and thickness, then the device structure is simple, but the 2DEG concentration cannot be optimized and on-resistance increases
Solution Approach 1:
The single barrier layer is segmented into two distinct barrier layers: a first barrier layer with higher Al content (20-40%) and greater thickness (30-50nm) to enhance 2DEG concentration, and a second barrier layer with lower Al content (5-20%) and smaller thickness (10-30nm) to stabilize threshold voltage. This segmentation allows independent optimization of each layer's properties to simultaneously improve on-resistance and threshold voltage stability.
Solution Approach 2:
Different regions of the device are assigned different barrier layer configurations: the active region uses the first barrier layer with high Al content for maximum 2DEG generation, while the gate region uses the second barrier layer with low Al content for stable threshold voltage. This local quality differentiation optimizes performance in each specific region according to its functional requirements.
2Manufacturing precision
If the Al component content and thickness of the barrier layer are increased to enhance 2DEG concentration, then on-resistance decreases, but threshold voltage becomes unstable and device reliability deteriorates
Solution Approach 1:
The barrier layer function is segmented between two layers: the first barrier layer (higher Al content, greater thickness) primarily serves to generate high 2DEG concentration for low on-resistance, while the second barrier layer (lower Al content, smaller thickness) primarily serves to stabilize threshold voltage through controlled depletion in the gate region.
Solution Approach 2:
The first barrier layer is localized to the active region where high 2DEG concentration is needed for low on-resistance, while the second barrier layer is localized to the gate region where threshold voltage stability is critical. Each layer's local properties are optimized for its specific functional role.
3Adaptability or versatility
If conventional single-step epitaxy is used to form the barrier layer, then the manufacturing process is simple, but the Al component content and thickness cannot be independently adjusted in different regions
Solution Approach 1:
The single epitaxy process is segmented into two sequential epitaxy steps: primary epitaxy forms the first barrier layer with high Al content across the entire wafer, then secondary epitaxy forms the second barrier layer with low Al content in the gate region. This segmentation enables independent control of Al content and thickness for each barrier layer type.
Solution Approach 2:
The epitaxy process parameters (Al content, thickness, temperature) are changed between the two epitaxy steps to create different barrier layer properties. The first epitaxy step uses high Al content parameters for the first barrier layer, while the second step uses low Al content parameters for the second barrier layer, enabling regional optimization.
4Reliability
If a single barrier layer configuration is used throughout the device, then manufacturing is easier, but etching damage and defects occur due to uniform high Al content
Solution Approach 1:
The barrier layer structure is designed with local quality differentiation: the first barrier layer with high Al content is confined to the active region where it provides strong 2DEG generation, while the second barrier layer with low Al content is placed in the gate region where it reduces etching damage and defect formation during subsequent processing steps.
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 method results in a GaN HEMT device with a lower on a stable and adjustable threshold voltage, and a lower on-resistance in the active region, reducing device loss and enhancing reliability.
Implementation Method 1
due to spontaneous and piezoelectric polarization effect of materials, after an aluminum gallium nitride (AlGaN) material is epitaxially grown on a GaN material, a two-dimensional electron gas (2DEG) with a high concentration and high mobility is generated
Implementation Method 2
due to spontaneous and piezoelectric polarization effect of materials
Implementation Method 3
the p-type cap layer is configured to deplete a two-dimensional electron gas formed by the second barrier layer and the channel layer
Implementation Method 4
The first barrier layer in the active region is formed through primary epitaxy, and then the second barrier layer that is in the gate region and different from the first barrier layer is formed through secondary epitaxy
Data Source
AI summary
Disclosed are an enhanced HEMT device and a preparing method thereof. The device includes a substrate, and a primary epitaxial structure and a secondary epitaxial structure that are grown on the substrate. The entire device may be divided into an active region and a gate region in a horizontal direction. The primary epitaxial structure includes a channel layer and a first barrier layer. The secondary epitaxial structure includes a second barrier layer and a p-type cap layer. The first barrier layer is on a part of the channel layer in the active region. The second barrier layer is on a part of the channel layer in the gate region. The second barrier layer is different from the first barrier layer.