GaN HEMT Barrier Layer Structure for Normally-Off Gate Formation
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Solution Overview
Problem
Conventional methods for fabricating GaN-based high electron mobility transistors (HEMTs) face challenges in maintaining the integrity of the threshold voltage and channel region during the etching process, leading to suboptimal 'normally off' operation and potential damage to the device structure.
Innovation Solution
A method involving the formation of a patterned mask on the barrier layer to define the gate electrode location, followed by the creation of a second barrier layer adjacent to the mask, and subsequent formation of the gate, source, and drain electrodes, while adjusting the thickness and aluminum concentration of the barrier layers to achieve a 'normally off' operation mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etching process is used to form gate electrode, then gate electrode can be formed, but the integrity of channel region and threshold voltage deteriorates
Solution Approach 1:
The barrier layer is segmented into two distinct parts: a first barrier layer that remains intact to preserve the channel region and threshold voltage, and a second barrier layer that is selectively removed to enable gate electrode formation. This segmentation allows the etching process to form the gate electrode without damaging the underlying channel structure.
Solution Approach 2:
The second barrier layer is extracted or removed from the structure adjacent to the mask, creating a localized region where the gate electrode can be formed without requiring aggressive etching that would damage the channel region. This extraction enables selective access for gate formation while protecting critical areas.
2Ease of operation
If barrier layer thickness and aluminum concentration are adjusted, then 'normally off' operation is achieved, but manufacturing complexity increases
Solution Approach 1:
Different regions of the barrier layer structure are assigned different properties: the first barrier layer maintains specific thickness and aluminum concentration to preserve threshold voltage and enable normally-off operation, while the second barrier layer has different characteristics optimized for gate electrode formation. This local differentiation achieves the desired operational mode without requiring complex overall device redesign.
Solution Approach 2:
The thickness and aluminum concentration parameters of the barrier layers are precisely controlled and adjusted to achieve the normally-off operation mode. By optimizing these parameters, the device achieves enhanced reliability and operational control while the manufacturing process remains manageable through standard semiconductor fabrication techniques.
Data Source
AI summary
A method for fabricating high electron mobility transistor (HEMT) includes the steps of: forming a buffer layer on a substrate; forming a barrier layer on the buffer layer; forming a gate dielectric layer on the barrier layer; forming a work function metal layer on the gate dielectric layer; patterning the work function metal layer and the gate dielectric layer; forming a gate electrode on the work function metal layer; and forming a source electrode and a drain electrode adjacent to two sides of the gate electrode.