SiC Power Transistor Heterostructure for Low-Resistance Gallium Oxide
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Solution Overview
Problem
Power transistors based on gallium oxide face high electrical resistance and high production costs due to the use of polycrystalline SiC substrates and gallium oxide donor substrates with smaller diameters, leading to inefficient thermal conductivity and electrical transitions.
Innovation Solution
A power transistor structure comprising a monocrystalline SiC layer with an AlGaN layer and a gallium oxide layer, where the AlGaN layer has a controlled aluminum-to-gallium ratio and dopant gradients to reduce electrical resistance, and optionally includes a GaN layer for further resistance reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polycrystalline SiC substrates are used for gallium oxide transistors, then thermal conductivity is improved, but electrical resistance at the SiC-gallium oxide interface increases
Solution Approach 1:
An AlGaN intermediate layer is introduced between the SiC substrate and the gallium oxide layer. This intermediary layer has a conduction band positioned between the conduction bands of SiC and gallium oxide, creating continuous energy band alignment and reducing interface electrical resistance while maintaining thermal conductivity through the SiC substrate.
Solution Approach 2:
A composite heterostructure is created consisting of multiple layers: SiC substrate, AlGaN intermediate layer, and gallium oxide active layer. This composite structure combines the thermal advantages of SiC with the electrical advantages of gallium oxide, achieving both low thermal resistance and low electrical resistance through proper material selection and interface engineering.
2Ease of manufacture
If gallium oxide donor substrates are used, then transistor production is enabled, but production costs increase and substrate diameter is reduced
Solution Approach 1:
The AlGaN layer serves as a mediator that enables the use of commercially available large-diameter SiC substrates instead of expensive, limited-size gallium oxide donor substrates. This intermediary layer facilitates epitaxial growth of gallium oxide on SiC, eliminating the need for donor substrates and enabling scalable production on cost-effective, large-area substrates.
Solution Approach 2:
The invention uses SiC substrates as a template or copy base instead of requiring authentic gallium oxide donor substrates. The AlGaN intermediate layer enables the copying of gallium oxide transistor structures onto SiC substrates, which are more readily available in large sizes and lower costs, thereby scaling production capability.
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 structure achieves low electrical resistance and continuous energetic transitions, enabling low-loss current flow and reducing production costs by utilizing monocrystalline SiC and controlled doping, enhancing thermal conductivity and efficiency.
Implementation Method 1
the conduction band of AlGaN is between the conduction bands of SiC and gallium oxide, and therefore the electrical resistance between SiC and gallium oxide is low
Implementation Method 2
depositing an AlGaN layer on a monocrystalline SiC layer by means of MOCVD
Implementation Method 3
depositing a gallium oxide layer on the AlGaN layer by means of MOCVD or HVPE
Data Source
AI summary
A power transistor. The power transistor has a monocrystalline SiC layer. An AlGaN layer is arranged on the monocrystalline SiC layer. A gallium oxide layer is arranged on the AlGaN layer.