SiC-GaN Interface Band Alignment for Low Forward Voltage
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Solution Overview
Problem
The energy barrier between silicon carbide and Group III nitride layers in semiconductor devices leads to increased forward voltage and reduced efficiency, and existing methods like dopant implantation and annealing complicate the process and potentially damage the crystal structure.
Innovation Solution
A conductive silicon carbide substrate with a conductive aluminum gallium nitride layer having a specific aluminum mole fraction that brings the conduction bands into close proximity, reducing the energy barrier without making the layer resistive, and maintaining minimal optical absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If dopant implantation and annealing are used to reduce the energy barrier, then the forward voltage is reduced, but the process complexity increases and crystal damage occurs
Solution Approach 1:
The patent extracts the dopant implantation and annealing steps from the process, replacing them with a direct epitaxial growth approach that achieves the same energy barrier reduction without the complex intermediate steps
Solution Approach 2:
The patent introduces an intermediate aluminum gallium nitride layer with graded aluminum composition between the silicon carbide substrate and the Group III nitride active layer, which mediates the energy barrier reduction while avoiding crystal damage
2Loss of energy
If high doping concentration is used in silicon carbide to lower the energy barrier, then the forward voltage is reduced, but crystal damage increases
Solution Approach 1:
The patent changes the parameter from doping concentration to aluminum mole fraction in the aluminum gallium nitride layer, achieving energy barrier reduction through compositional grading rather than high doping, thus maintaining crystal quality
Solution Approach 2:
The aluminum gallium nitride layer with graded aluminum content serves as an intermediary that gradually transitions the band structure, reducing the energy barrier without requiring high doping concentrations that would damage the crystal
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
This approach effectively reduces the forward voltage across the interface, enhancing the efficiency of semiconductor devices like LEDs while minimizing crystal damage and process complexity.
Implementation Method 1
The aluminum gallium nitride layer has a mole fraction of aluminum that is sufficient to bring the conduction bands of the conductive substrate and the aluminum gallium nitride into close proximity
Data Source
AI summary
A structure is disclosed that reduces the forward voltage across the interface between silicon carbide and Group III nitride layers. The structure includes a conductive silicon carbide substrate and a conductive layer of aluminum gallium nitride on the silicon carbide substrate. The aluminum gallium nitride layer has a mole fraction of aluminum that is sufficient to bring the conduction bands of the silicon carbide substrate and the aluminum gallium nitride into close proximity, but less than a mole fraction of aluminum that would render the aluminum gallium nitride layer resistive.