GaN-SiC Heterojunction Diode for Power Applications
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Solution Overview
Problem
Conventional semiconductor devices for power applications, such as silicon-employed P-N junction diodes and Schottky barrier diodes, fail to meet requirements for low leakage current, high breakdown voltage, large output current, short reverse recovery time, and high peak surge current due to material limitations and manufacturing challenges with wide band gap semiconductor materials like SiC and group-III nitride semiconductors.
Innovation Solution
A semiconductor device comprising a P-N junction structure with an n-type group-III nitride layer and a p-type group-IV semiconductor layer, forming a heterojunction with a Schottky contact, which reduces reverse leakage current and enhances breakdown voltage, output current, and reverse recovery time, while avoiding the limitations of SiC and group-III nitride manufacturing issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon-employed P-N junction diode is used, then it is easy to manufacture, but it has long reverse recovery time due to carrier injection from both P and N sides
Solution Approach 1:
The patent employs a heterojunction structure combining group-III nitride semiconductor (GaN) with a wider band gap and silicon carbide (SiC) with a narrower band gap. This composite material approach allows the GaN side to block reverse current effectively (reducing reverse recovery time) while the SiC side provides good manufacturability and electrical properties, resolving the contradiction between ease of manufacture and reverse recovery time.
2Loss of time
If a silicon-employed Schottky barrier junction diode is used, then reverse current at shutoff does not occur, but it has large leakage current and low breakdown voltage at reverse-bias voltage
Solution Approach 1:
The heterojunction combines GaN (wider band gap) and SiC (narrower band gap) to achieve both low reverse leakage current and high breakdown voltage. The GaN layer provides excellent reverse blocking characteristics with minimal leakage current, while the SiC layer contributes to higher breakdown voltage and better thermal stability, thus resolving the contradiction between reverse recovery performance and breakdown voltage.
Solution Approach 2:
The patent utilizes the difference in band gap parameters between GaN and SiC materials. By carefully selecting and controlling the band gap parameters through material composition and doping, the device achieves optimal balance between leakage current suppression and breakdown voltage enhancement.
3Reliability
If SiC single crystal is used, then breakdown voltage increases, but it has many crystal defects (micropipes) making it difficult to manufacture stable devices with sufficient output current
Solution Approach 1:
The patent uses a heterojunction structure where GaN and SiC layers complement each other. The GaN layer provides high breakdown voltage capability, while the SiC layer offers superior crystalline quality and manufacturing stability. This composite approach allows the device to achieve high breakdown voltage without suffering from the micropipe defects inherent in SiC single crystal, thus resolving the contradiction between breakdown voltage and manufacturing stability.
4Power
If a P-N junction diode employing SiC is used, then it can handle power applications, but carrier recombination from crystal defects limits output current
Solution Approach 1:
The heterojunction structure combines GaN and SiC materials where each layer performs its strength. The GaN layer with wider band gap provides excellent carrier blocking and high power handling capability, while the SiC layer with narrower band gap and superior crystalline quality minimizes carrier recombination losses. This composite material approach resolves the contradiction between power handling capability and output current by allowing each material to contribute its optimal properties.
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 semiconductor device achieves small leakage current, high breakdown voltage, large output current, short reverse recovery time, and high peak surge current, improving upon the limitations of existing silicon and SiC-based devices with a stable and efficient power inverter or converter circuit.
Implementation Method 1
a first semiconductor layer made of a group-III nitride having a composition of Al1-x-yGaxInyN (x≧0, y≧0, 0≦x+y≦1); a second semiconductor layer joined to the first semiconductor layer at a first junction, the second semiconductor layer having a second conductivity type different from the first conductivity type
Data Source
AI summary
A semiconductor device having small leakage current and high breakdown voltage during reverse blocking, small on-state resistance and large output current at forward conduction, short reverse recovery time at shutoff, and high peak surge current value is provided. An n-type layer is made of a group-III nitride, and a p-type layer is made of a group-IV semiconductor material having a smaller band gap than the group-III nitride. The energy level at the top of the valence band of the n-type layer is lower than the energy level at the top of the valence band of the p-type layer, so that a P-N junction semiconductor device satisfying the above requirements is obtained. Further, a combined structure of P-N junction and Schottky junction by additionally providing an anode electrode to be in Schottky contact with the n-type layer also achieves the effect of decreasing voltage at the rising edge of current resulting from the Schottky junction.