Hybrid GaN Schottky Diode Structure for Low Turn-On and High Breakdown
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Solution Overview
Problem
High breakdown field in wide bandgap semiconductors like GaN is challenging to achieve within devices due to high on-state power loss in p-n diodes, while Schottky diodes offer low turn-on voltage but with limited maximum field, and the introduction of high permittivity dielectrics increases turn-on voltage.
Innovation Solution
A hybrid Schottky diode design where the forward characteristics are determined by the metal-semiconductor junction and reverse characteristics and breakdown by the metal/dielectric/semiconductor junction, utilizing a high-K dielectric with a dielectric constant greater than 25 disposed between the anode and cathode to achieve low turn-on voltage and high breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a p-n junction is used to achieve high breakdown voltage, then breakdown voltage is improved, but turn-on voltage increases causing higher on-state power loss
Solution Approach 1:
The device is segmented into two separate junctions: a Schottky junction for low-voltage forward conduction and a p-n junction for high-voltage reverse blocking. This segmentation allows each junction to optimize its function independently, achieving low turn-on voltage through the Schottky contact while maintaining high breakdown voltage through the p-n junction.
Solution Approach 2:
Different regions of the device have different functional qualities: the metal-semiconductor contact region provides low turn-on voltage characteristics, while the p-n junction region provides high breakdown voltage characteristics. This local differentiation of quality allows simultaneous optimization of both contradictory requirements.
2Use of energy by moving object
If a Schottky diode is used to achieve low turn-on voltage, then turn-on voltage is improved, but maximum field is limited by metal/semiconductor barrier height
Solution Approach 1:
The device separates the functions of low turn-on voltage and high maximum field into different junctions. The Schottky junction handles forward conduction with low turn-on voltage, while the p-n junction handles reverse blocking with high maximum field capability.
Solution Approach 2:
The p-n junction acts as an intermediary that enables the Schottky diode to achieve higher breakdown voltages than would be possible with the metal-semiconductor barrier alone. The p-n junction provides the additional field sustainment capability.
3Strength
If high permittivity dielectrics are introduced to increase breakdown voltage, then breakdown voltage is improved, but turn-on voltage increases
Solution Approach 1:
The device segments the breakdown enhancement function from the turn-on voltage determination. The p-n junction provides breakdown voltage enhancement without affecting the Schottky junction turn-on characteristics, avoiding the turn-on voltage increase associated with high permittivity dielectrics.
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 hybrid Schottky diode demonstrates significant improvement in breakdown performance with average breakdown fields up to 2.22 MV/cm and reduced turn-on voltage of 0.47 V, enabling state-of-the-art power switching figures of merit for GaN lateral Schottky diodes.
Implementation Method 1
Recently, it was shown that high dielectric permittivity heterojunctions reduce the field at the metal Schottky barrier and make electric fields uniform in the depletion region, thus enabling higher average fields and breakdown voltage.
Implementation Method 2
Schottky diodes provide the advantage of low turn on voltage, but the maximum field achievable is limited by the metal/semiconductor barrier height.
Implementation Method 3
high dielectric permittivity heterojunctions reduce the field at the metal Schottky barrier and make electric fields uniform in the depletion region
Data Source
AI summary
A hybrid Schottky diode is described herein where the forward characteristics are determined by the metal-semiconductor junction, and the reverse characteristics and breakdown are determined by the metal/dielectric/semiconductor junction. Experimental demonstration of such hybrid Schottky diodes shows significant improvement in the breakdown performance with average breakdown field up to 2.22 MV/cm with reduced turn on of 0.47 V and enable state-of-art power switching figure of merit for GaN lateral Schottky diodes.