MPS Diode Buffer Layer for Lower Leakage and Conduction Loss
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Solution Overview
Problem
Existing SiC Schottky Barrier Diodes (SBDs) face challenges in balancing reverse leakage current and forward operating bias, as increasing the Schottky barrier height to reduce leakage current leads to increased forward conduction loss, and vice versa.
Innovation Solution
The MPS diode device incorporates a buffer layer with a larger band gap than the epitaxial layer, made of allotropic material, to modulate the Schottky barrier height and reduce lattice mismatch, thereby reducing both forward conduction loss and reverse leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the Schottky barrier height is increased to reduce reverse leakage current, then reverse leakage current is reduced, but forward conduction loss increases
Solution Approach 1:
The patent introduces a buffer layer with different material composition and band gap characteristics at the Schottky junction interface, creating local quality variation. This buffer layer (e.g., AlGaN with higher Al content) has wider band gap than the epitaxial layer, which locally modifies the Schottky barrier properties to reduce reverse leakage without significantly increasing forward conduction loss.
Solution Approach 2:
The patent employs composite material structure consisting of multiple layers with different compositions (e.g., AlGaN buffer layer on GaN epitaxial layer). The composite structure combines the advantages of different materials: the buffer layer provides high reverse blocking capability while the epitaxial layer maintains good forward conduction characteristics.
2Loss of energy
If a buffer layer with larger band gap is introduced to modulate Schottky barrier height, then forward conduction loss is reduced, but device structure complexity increases
Solution Approach 1:
The patent modifies the band gap parameter by selecting buffer layer material with larger band gap than the epitaxial layer (e.g., AlGaN with higher Al mole fraction). This parameter change enables Schottky barrier height modulation, allowing the buffer layer to reduce forward conduction loss while maintaining reverse blocking performance.
Solution Approach 2:
The buffer layer acts as an intermediary between the metal electrode and the epitaxial layer. It mediates the interface properties, reducing lattice mismatch and dislocation density, while also providing band gap engineering capability to optimize both forward and reverse characteristics.
3Object-generated harmful factors
If allotropic material is used for buffer layer to reduce lattice mismatch, then interface state is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses allotropic materials (e.g., 4H-SiC buffer on 3C-SiC epitaxial layer) that have the same chemical composition but different crystal structures. This homogeneity in chemical composition reduces lattice mismatch at the interface, minimizing interface states and dislocations while maintaining good epitaxial growth conditions.
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 MPS diode device achieves reduced conduction loss in the forward bias direction and decreased leakage current in the reverse bias direction, enhancing overall performance by balancing these parameters.
Implementation Method 1
a buffer layer with a larger band gap than the epitaxial layer, to modulate the Schottky barrier height and reduce lattice mismatch
Implementation Method 2
since the buffer layer is made of a allotropic material with the epitaxial layer the stress problem from lattice mismatch at the interface between the buffer layer and the epitaxial layer can be greatly improved
Implementation Method 3
the interface state can be greatly reduced and the leakage current in the reverse bias direction of the MPS diode device can also be reduced
Data Source
AI summary
Disclosed are an MPS diode device and a preparation method therefor. The MPS diode device comprises a plurality of cells arranged in parallel, wherein each cell comprises a cathode electrode, and a substrate, epitaxial layer, buffer layer, and anode electrode that are formed in succession on the cathode electrode; two active regions are formed on the side of the epitaxial layer away from the substrate; the width of forbidden band of the buffer layer is greater than the width of forbidden band of the epitaxial layer, and a material of the buffer layer and a material of the epitaxial layer are allotropes; and first openings are formed at the positions in the buffer layer opposite to the active regions, and an ohmic metal layer is formed in the first openings.