GaN-HEMT Hydrophobic Layer Suppresses Current Collapse
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Solution Overview
Problem
GaN-HEMTs experience current collapse due to electron traps at the semiconductor surface and surface passivation film, leading to decreased current and output under voltage stress.
Innovation Solution
A hydrophobic layer containing Si-CxHy is formed on the surface of the first protection film using a silylation process, which reduces water adsorption and suppresses current collapse by replacing Si-OH groups with Si-CxHy, improving the film's water repellency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a surface passivation film is formed on the compound semiconductor layer, then the semiconductor surface is protected, but electron traps are created at the interface causing current collapse
Solution Approach 1:
The patent applies local quality by creating a hydrophobic layer specifically at the surface of the protection film where electron traps are most problematic. This localized modification changes the chemical properties (making it hydrophobic) only at the critical interface region, reducing water adsorption and electron trap effects precisely where they cause current collapse, while leaving the bulk protection film properties intact.
Solution Approach 2:
The patent changes the chemical composition parameter of the protection film surface by forming Si-CxHy bonds through silylation. This parameter change transforms the surface from hydrophilic to hydrophobic, fundamentally altering its interaction with water molecules and reducing the formation of electron traps at the semiconductor-protection film interface.
2Strength
If the protection film surface is made hydrophilic, then adhesion is improved, but water adsorption increases causing current collapse
Solution Approach 1:
The hydrophobic layer is applied locally at the outer surface of the protection film, creating a gradient structure where the inner interface maintains good adhesion while the outer surface exhibits water repellency. This localized modification resolves the contradiction by having different regions serve different functions.
Solution Approach 2:
The structure becomes a composite system with the protection film providing mechanical adhesion and the hydrophobic surface layer providing water repellency. This composite approach allows both adhesion strength and water adsorption resistance to be optimized simultaneously through the combination of different material properties at different depths.
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 hydrophobic layer effectively reduces current degradation caused by bias stress, improving the reliability and withstand voltage of AlGaN/GaN-HEMTs by minimizing hydroxyl group and adsorbed water effects.
Implementation Method 1
forming a hydrophobic layer which contains Si—CxHy at a surface of the first protection film by performing a silylation process for Si—OH existing at the surface of the first protection film by using a silane compound
Implementation Method 2
A hydrophobic layer containing Si—CxHy is formed at a surface of the first protection film
Data Source
AI summary
A compound semiconductor device includes a first protection film which covers a surface of a compound semiconductor layer, where the first protection film is an insulating film whose major constituent is Si and at least one element between N and O, and a hydrophobic layer containing Si—CxHy is formed at a surface thereof.