GaN Diode Anode Segmentation for Leakage Reduction
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Solution Overview
Problem
Schottky diodes using AlGaN/GaN heterostructures face increased reverse leakage current when a passivation film is formed, which contradicts the goal of reducing this current, and the existing method of using metals with different Schottky barrier heights is insufficient in achieving low conduction loss.
Innovation Solution
The diode design includes a p-type nitride semiconductor layer, a first metal layer in ohmic contact with the p-type nitride semiconductor layer, and a second metal layer in ohmic contact with the channel, which interrupts the leakage path formed between the passivation film and the semiconductor layer stack, reducing reverse leakage current and allowing for adjustment of the forward threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation film is formed to prevent impurities and reduce surface states, then device reliability is improved, but reverse leakage current increases significantly
Solution Approach 1:
The anode electrode is segmented into a first metal layer and a second metal layer with different functions. The first metal layer forms a Schottky barrier to block reverse leakage current, while the second metal layer provides low resistance for forward current, thus resolving the contradiction between preventing leakage and maintaining conductivity.
Solution Approach 2:
Different regions of the anode electrode are assigned different properties: the first metal layer has high Schottky barrier height for blocking reverse current, while the second metal layer has low Schottky barrier height for efficient forward conduction. This local differentiation allows simultaneous achievement of low leakage and low conduction loss.
2Object-generated harmful factors
If metals with different Schottky barrier heights are used to reduce reverse leakage current, then reverse leakage is reduced, but conduction loss cannot be sufficiently reduced
Solution Approach 1:
The anode electrode is divided into two functional metal layers: the first metal layer with high Schottky barrier height blocks reverse leakage current, while the second metal layer with low Schottky barrier height enables efficient forward current flow, thereby reducing both reverse leakage and conduction loss simultaneously.
Solution Approach 2:
The Schottky barrier height parameter is optimized by using different metal materials with specifically selected work functions. The first metal layer uses materials with high work function for blocking, while the second metal layer uses materials with low work function for conduction, achieving optimal balance between leakage reduction and conduction efficiency.
3Loss of energy
If the forward threshold voltage is reduced to decrease conduction loss, then conduction efficiency is improved, but reverse leakage current increases
Solution Approach 1:
The anode electrode structure is segmented into first and second metal layers that independently control reverse blocking and forward conduction characteristics. This segmentation allows the forward threshold voltage to be reduced by optimizing the second metal layer without compromising reverse leakage blocking provided by the first metal layer.
Solution Approach 2:
Different local regions of the anode electrode are optimized for different functions: the first metal layer is optimized for high barrier height to block reverse current, while the second metal layer is optimized for low barrier height to reduce forward conduction loss, achieving local optimization of electrical characteristics.
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 reverse leakage current by several orders of magnitude compared to traditional Schottky diodes, both with and without a passivation film, while maintaining low on-resistance and conduction loss, and allows for precise adjustment of the forward threshold voltage.
Implementation Method 1
a p-type nitride semiconductor layer, a first metal layer being in ohmic contact with the p-type nitride semiconductor layer, and a second metal layer connected to the first metal layer, and being in ohmic contact with a channel
Implementation Method 2
a first metal layer being in ohmic contact with the p-type nitride semiconductor layer, and a second metal layer connected to the first metal layer, and being in ohmic contact with a channel
Data Source
AI summary
A diode includes: a semiconductor layer stack; cathode and anode electrodes formed on the semiconductor layer stack so as to be spaced apart from each other; and a protection film covering a region of an upper surface of the semiconductor layer stack. The semiconductor layer stack includes a first nitride semiconductor layer, and a second nitride semiconductor layer having a larger band gap than the first nitride semiconductor layer, and has a channel. The anode electrode includes: a p-type third nitride semiconductor layer formed on the semiconductor layer stack; a first metal layer being in ohmic contact with the third nitride semiconductor layer; and a second metal layer being in contact with the first metal layer, and being in ohmic contact with the channel.