HEMT Barrier Layer Layout for Uniform Threshold Voltage
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face challenges in controlling the threshold voltage and ON-current level due to non-uniform distribution of the gate electric field, leading to hump-like characteristics in drain current and gate voltage curves, which complicates their application in power devices.
Innovation Solution
The design includes a channel layer with 2-dimensional electron gas (2DEG) and a barrier layer with varying thickness and recesses to induce different 2DEG densities, along with a depletion formation layer and specific edge regions, allowing for a uniform electric field distribution and hump-free current-voltage characteristics by forming channels in both edge and central regions at the same threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional HEMT structure with uniform barrier layer is used, then the manufacturing process is simple, but the gate electric field distribution is non-uniform causing hump-like characteristics in current-voltage curves
Solution Approach 1:
The barrier layer is designed with different thicknesses in different regions: a first thickness in the central region and a second thickness in the edge regions. This local variation in barrier layer thickness creates corresponding variations in 2DEG density, which compensates for the non-uniform gate electric field distribution and eliminates the hump-like characteristics in the current-voltage curves.
2Manufacturing precision
If the barrier layer thickness is varied to improve electric field distribution, then the current-voltage characteristics improve, but the manufacturing process complexity increases
Solution Approach 1:
The barrier layer is segmented into distinct thickness regions: a central region with a first thickness and edge regions with a second thickness. This segmentation allows for controlled variation in 2DEG density across different areas of the device, enabling uniform electric field distribution while maintaining a relatively straightforward manufacturing process using standard semiconductor fabrication techniques.
3Ease of operation
If recesses are formed in the barrier layer to create different 2DEG densities, then the threshold voltage control improves, but the manufacturing steps increase
Solution Approach 1:
Recesses are formed locally in the barrier layer at the edge regions, creating areas with different 2DEG densities compared to the central region. This local modification allows for precise control of the threshold voltage by adjusting the depth and dimensions of the recesses, while the rest of the barrier layer maintains its original structure, thus limiting the increase in manufacturing complexity to specific process 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 approach enables improved operating characteristics of HEMTs with a hump-free current-voltage curve, facilitating their use in power devices by ensuring consistent and efficient current flow.
Implementation Method 1
An HEMT includes semiconductors having different electrical polarization characteristics from each other. In an HEMT, a semiconductor layer having a relatively large polarization rate may induce a 2-dimensional electron gas (Hereinafter, 2DEG) in another semiconductor layer contacted thereto.
Data Source
AI summary
Provided is a high electron mobility transistor including: a channel layer comprising a 2-dimensional electron gas (2DEG); a barrier layer on the channel layer and comprising first regions and a second region, the first regions configured to induce the 2DEG of a first density in portions of the channel layer and the second region configured to induce the 2DEG of a second density different from the first density in other portions of the channel layer; source and drain electrodes on the barrier layer; a depletion formation layer formed on the barrier layer between the source and drain electrodes to form a depletion region in the 2DEG; and a gate electrode on the barrier layer. The first regions may include a first edge region and a second edge region corresponding to both ends of a surface of the gate electrode facing the channel layer.