Schottky Diode Anode Segmentation for Leakage Reduction
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Solution Overview
Problem
Schottky diodes on AlGaN/GaN heterostructures suffer from high leakage current when reverse biased, leading to power losses due to incomplete depletion of the 2DEG layer under the Schottky contact, and existing solutions either increase resistance or capacitance in forward bias mode.
Innovation Solution
A Schottky diode structure with a dielectric layer between the anode and the upper III-nitride layer, configured to pinch off the 2DEG layer in reverse bias mode, comprising a first portion directly adjoining the anode and a second portion separated from the anode by a thin dielectric material, minimizing anode size and forward bias resistance while reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a Schottky diode is formed on AlGaN/GaN heterostructure with standard structure, then forward voltage drop is low and switching speed is fast, but leakage current is high in reverse bias mode
Solution Approach 1:
The anode is divided into two distinct portions: a first portion that directly contacts the AlGaN layer to form a Schottky barrier, and a second portion that is separated from the AlGaN layer by a dielectric material. This segmentation allows the first portion to handle forward conduction while the second portion, isolated by the dielectric, creates a depletion region that pinches off the 2DEG layer in reverse bias, thereby reducing leakage current without increasing forward resistance
Solution Approach 2:
A dielectric material layer is introduced as an intermediary between the second portion of the anode and the AlGaN layer. This dielectric layer has a thickness of 2-30nm and serves as a mediator that electrically isolates the second anode portion from the 2DEG layer while still allowing the structure to benefit from the high breakdown voltage of GaN. The dielectric acts as a barrier that prevents direct carrier injection in reverse bias, reducing leakage current
2Reliability
If the anode is completely separated from the upper III-nitride layer by dielectric material to reduce leakage, then reverse bias leakage current decreases, but forward bias resistance increases
Solution Approach 1:
The anode is segmented into two portions with different functions: the first portion maintains direct contact with the AlGaN layer to provide low-resistance path for forward current, while the second portion is separated by dielectric to reduce reverse leakage. This segmentation resolves the contradiction by allowing each portion to optimize for its specific bias condition
Solution Approach 2:
Different regions of the anode structure are given different properties: the first portion has direct metal-semiconductor contact for low forward resistance, while the second portion has dielectric isolation for reverse leakage suppression. The local quality varies spatially to meet different functional requirements in different operating conditions
3Reliability
If a thick dielectric layer is used to completely isolate the anode from the upper III-nitride layer, then leakage current is reduced, but device capacitance increases
Solution Approach 1:
The dielectric layer thickness is precisely controlled within the range of 2-30nm, which is thin enough to minimize capacitance effects but thick enough to provide adequate electrical isolation and pinch-off of the 2DEG layer. This parameter optimization resolves the contradiction between leakage reduction and capacitance minimization
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 dielectric layer effectively pinches off the 2DEG layer in reverse bias mode, significantly reducing leakage current and maintaining low resistance and capacitance in forward bias mode, thereby minimizing power losses.
Implementation Method 1
the dielectric material being configured to pinch off the 2DEG layer in the reverse bias region of the diode
Implementation Method 2
the high mobility and high electron density of the 2DEG-layer (2-dimensional electron gas) appearing between the GaN and the AlGaN layer as a result of the difference of piezoelectric and spontaneous polarization
Implementation Method 3
the high mobility and high electron density of the 2DEG-layer (2-dimensional electron gas) appearing between the GaN and the AlGaN layer as a result of the difference of piezoelectric and spontaneous polarization
Implementation Method 4
an anode comprising a first portion that forms a Schottky barrier contact with the upper III-nitride layer
Data Source
Figure 1a~1b
Figure 2
Figure 3a~3b
AI summary
The present invention is related to a Schottky diode device comprising ● at least a lower and an upper III-nitride layer (4,5) forming a heterojunction therebetween, ● a 2DEG layer (6) forming or obtainable in the lower of the two layers, so that a 2DEG layer may be formed in the lower of the two layers, ● an anode (11) comprising a first portion (15) that forms a Schottky barrier contact (10) with the upper III-nitride layer and a second portion (16) that is separated from the upper III-nitride layer by a layer of dielectric material (17), the second portion being located between the anode and the cathode, the dielectric material being configured to pinch off the 2DEG layer in the reverse bias region of the diode, said first and second portion being directly adjoining, ● a passivation area (7) isolating the anode and cathode from each other. The invention is equally related to a method for producing a device of the invention, possibly in an integrated process for producing a Schottky diode and a HEMT transistor.