GaN HEMT Insulating Film Stack Suppresses Current Collapse
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Solution Overview
Problem
Current GaN-based high electron mobility transistors (HEMTs) face a current collapse issue due to electrons being trapped by insulating films, which interferes with the flow of two-dimensional electron gas and decreases output current, with no effective technique available to suppress this phenomenon.
Innovation Solution
A compound semiconductor device structure is developed with a layered structure including a first protective insulating film of silicon nitride, a second protective insulating film of silicon oxide, and a third protective insulating film containing silicon oxynitride, formed between the first and second films to suppress current collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film is used to cover the gate electrode for protection, then the device structure is improved and protected, but current collapse occurs due to electron trapping which decreases output current
Solution Approach 1:
The protective insulating film is divided into multiple layers with different materials (first insulating film, second insulating film, and third insulating film) to perform different functions. The first layer provides basic protection, the second layer prevents electron trapping, and the third layer suppresses current collapse, thereby resolving the contradiction between protection and harmful effects.
Solution Approach 2:
The patent uses a composite structure of multiple insulating films with different material properties. By combining materials with different characteristics (such as different dielectric constants, electron trapping properties, and current collapse suppression capabilities), the system achieves both protective coverage and prevention of current collapse.
2Reliability
If a protective insulating film is formed on the compound semiconductor layered structure, then device protection is improved, but Si dangling bonds at the interface cause current collapse
Solution Approach 1:
The third insulating film acts as an intermediary layer between the first and second insulating films. This intermediate layer specifically addresses the Si dangling bonds at the interface by providing a material composition that bonds with or passivates the dangling bonds, thereby preventing current collapse while maintaining device protection.
Solution Approach 2:
The patent changes the material parameters of the insulating films, specifically introducing a third film with different compositional parameters (oxynitride composition) between the silicon nitride and silicon oxide layers. This parameter change enables the third film to interact with Si dangling bonds and suppress current collapse.
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 proposed structure effectively suppresses current collapse, improving the reliability and high-withstand-voltage performance of AlGaN/GaN HEMTs by relaxing Si dangling bonds at the interface between the insulating films, thereby enhancing device characteristics.
Implementation Method 1
Two-dimensional electron gas (2DEG) of high concentration is obtained from piezoelectric polarization and spontaneous polarization of AlGaN caused by the strain.
Data Source
AI summary
A compound semiconductor device includes: a compound semiconductor layered structure; a gate electrode formed above the compound semiconductor layered structure; a first protective insulating film that covers a surface of the compound semiconductor layered structure and is made of silicon nitride as a material; a second protective insulating film that covers the gate electrode on the first protective insulating film and is made of silicon oxide as a material; and a third protective insulating film that contains silicon oxynitride and is formed between the first protective insulating film and the second protective insulating film.