GaN Schottky Diode Termination Structure for Field Crowding
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Solution Overview
Problem
Nitride-based Schottky diodes face challenges in achieving vertical conduction due to insulating substrates, leading to higher turn-on resistance and electric field crowding issues, particularly in high-voltage applications, where conventional termination structures are ineffective due to lattice mismatch and high material costs.
Innovation Solution
A termination structure comprising a P-type nitride-based epitaxial guard ring and dielectric field plate is formed at the edge of the anode electrode, with a step recess to enhance field spreading, reducing electric field crowding and improving breakdown voltage, and a silicon-based PN junction diode is connected in parallel to divert avalanche current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a lateral conduction path is used in nitride-based Schottky diodes due to insulating substrates, then the device can be manufactured on low-cost substrates like silicon or sapphire, but the turn-on resistance increases and current distribution becomes non-uniform
Solution Approach 1:
The patent transitions from lateral conduction to vertical conduction by changing the current path dimension. The anode electrode is positioned on the front surface while the cathode electrode is formed on the back surface of the semiconductor body, creating a vertical current path that reduces resistance and improves current uniformity while maintaining compatibility with insulating substrates
2Device complexity
If conventional termination structures are used in nitride-based Schottky diodes, then the structure can be simplified, but electric field crowding at the anode electrode edge increases, reducing breakdown voltage
Solution Approach 1:
The patent introduces a termination structure comprising a P-type epitaxial guard ring and dielectric field plate as intermediary elements between the anode electrode edge and the semiconductor body. This structure spreads the electric field and reduces field crowding, enabling high breakdown voltage while maintaining a practical device design
Solution Approach 2:
The termination structure is specifically positioned at the critical region (anode electrode edge) where electric field crowding occurs. The P-type guard ring and dielectric field plate create localized field management exactly where needed, improving breakdown voltage without affecting other device regions
3Reliability
If bulk GaN substrate is used to achieve best device performance, then the epitaxial layer quality is optimized, but the material cost becomes prohibitively high
Solution Approach 1:
The patent replaces expensive bulk GaN substrates with low-cost insulating substrates (silicon, sapphire, or SiC). While the substrate itself is not disposable, this substitution strategy uses affordable substrate materials that can be mass-produced, dramatically reducing material cost while maintaining adequate device performance through proper epitaxial growth and device design
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 enables vertical conduction in nitride-based Schottky diodes, reducing turn-on resistance and enhancing reliability and UIS capability by effectively managing electric fields and avalanche currents.
Implementation Method 1
The termination structure is configured to reduce electric field crowding at the edge of the anode electrode
Implementation Method 2
a silicon-based PN junction diode is connected in parallel to divert avalanche current
Data Source
AI summary
A termination structure for a nitride-based Schottky diode includes a guard ring formed by an epitaxially grown P-type nitride-based compound semiconductor layer and dielectric field plates formed on the guard ring. The termination structure is formed at the edge of the anode electrode of the Schottky diode and has the effect of reducing electric field crowding at the anode electrode edge, especially when the Schottky diode is reverse biased. In one embodiment, the P-type epitaxial layer includes a step recess to further enhance the field spreading effect of the termination structure.