GaN HEMT Gate Umbrella Structure for Current Collapse Reduction
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Solution Overview
Problem
Nitride semiconductor devices, particularly AlGaN/GaN HEMTs, face current collapse issues due to electric field concentration at the gate electrode, leading to degraded performance in high-voltage applications.
Innovation Solution
A compound semiconductor device with a gate recess structure and a Schottky contact is designed, incorporating a gate umbrella portion and a dielectric structure to alleviate electric field concentration, maintaining a high threshold value and improving current collapse characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate electrode structure is used in nitride semiconductor devices, then the device structure is simple, but electric field concentration occurs at the gate electrode leading to current collapse
Solution Approach 1:
The gate electrode is divided into two distinct portions: a gate base portion embedded in the semiconductor layer and a gate umbrella portion extending upward. This segmentation allows each portion to serve different functions - the base portion provides electrical connection while the umbrella portion creates a Schottky contact to control the electric field distribution, thereby reducing field concentration and current collapse
Solution Approach 2:
A gate insulating film is introduced as an intermediary layer between the gate base portion and the gate umbrella portion. This insulating film enables the formation of a MIS-type structure that controls the electric field at the gate, preventing direct metal-to-semiconductor contact and reducing field concentration effects
2Reliability
If the gate electrode is modified to reduce electric field concentration, then current collapse characteristics improve, but the manufacturing process becomes more complex
Solution Approach 1:
The gate recess structure is formed in advance before depositing the gate electrode materials. This preliminary action creates the necessary geometric configuration that allows subsequent electrode layers to self-align and form the umbrella structure, simplifying the overall manufacturing process despite the added structural complexity
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 solution effectively reduces current collapse and enhances device efficiency and breakdown voltage in nitride semiconductor devices, making them suitable for high-power and high-frequency applications.
Implementation Method 1
a surface of the gate umbrella portion includes a Schottky contact with the compound semiconductor multilayer structure
Implementation Method 2
Highly concentrated two dimensional electron gas (2DEG) may be obtained based on the piezoelectric polarization and spontaneous polarization of AlGaN
Implementation Method 3
Highly concentrated two dimensional electron gas (2DEG) may be obtained based on the piezoelectric polarization and spontaneous polarization of AlGaN
Data Source
AI summary
A compound semiconductor device includes: a compound semiconductor multilayer structure; a gate insulating film on the compound semiconductor multilayer structure; and a gate electrode, wherein the gate electrode includes a gate base portion on the gate insulating film and a gate umbrella portion, and a surface of the gate umbrella portion includes a Schottky contact with the compound semiconductor multilayer structure.