Diamond FET Gate Interface Using C-Si Bonds to Cut Trap Density
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Solution Overview
Problem
The interface state density in diamond field effect transistors (FETs) increases due to C—O bonds at the interface between the gate insulating film and the diamond substrate, hindering their practical application in high-power power devices, and there is a lack of evaluation on using a silicon oxide film as a gate insulating film on diamond surfaces.
Innovation Solution
A diamond field effect transistor is developed with a silicon-terminated layer containing C—Si bonds at the interface between the diamond layer and the gate insulating film, using a silicon oxide film as the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon oxide film is formed as a gate insulating film on a diamond substrate via C—O bonds, then the interface state density increases, but using C—Si bonds instead reduces the interface state density
Solution Approach 1:
A silicon-terminated layer is introduced as an intermediary between the diamond substrate and the silicon oxide gate insulating film. This intermediate layer forms C—Si bonds with the diamond substrate, preventing direct C—O bond formation and reducing interface state density, thereby improving device reliability
Solution Approach 2:
The gate insulating film structure is designed as a composite system comprising a silicon-terminated layer and a silicon oxide film. This composite structure combines the benefits of stable C—Si bonding at the interface with the high reliability of silicon oxide as the gate insulator
2Reliability
If Al2O3 (alumina) is used as a gate insulating film, then the device can operate, but the chemical bond structure is less stable compared to SiO2
Solution Approach 1:
The gate insulating film material is changed from Al2O3 to SiO2, utilizing the superior chemical bond stability of SiO2. This parameter change in material composition enhances the overall reliability and stability of the diamond FET device
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 configuration reduces the interface state density, enabling the transistor to operate as a normally-off enhancement-type FET suitable for high-voltage and high-current applications.
Implementation Method 1
a silicon-terminated layer containing C—Si bonds formed of bonds between carbon atoms and silicon atoms is provided at an interface between the first diamond layer and the gate insulating film
Data Source
AI summary
Provided are a diamond field effect transistor using a silicon oxide film as a gate insulating film including a silicon-terminated layer containing C—Si bonds in order to reduce an interface state density, and a method for producing the same. A FET 100A includes a silicon oxide film 3A formed on a surface of a non-doped diamond layer 2A, a non-doped diamond layer 4A formed on a surface of the non-doped diamond layer 2A using the silicon oxide film 3A as a mask, a silicon-terminated layer 5A formed at an interface between the non-doped diamond layer 2A and the silicon oxide film 3A and at an interface between the non-doped diamond layer 4A and the silicon oxide film 3A, and a gate electrode 12A formed on the silicon oxide film 3A. The FET 100A operates using the silicon oxide film 3A and an insulating film 10A formed on the silicon oxide film 3A as a gate insulating film 11A and using the non-doped diamond layer 4A as each of a source region and a drain region.