Stress Controlling Layer for AlGaN Heterostructures
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Solution Overview
Problem
The fabrication of high-quality aluminum gallium nitride (AlGaN) layers is challenged by threading dislocations resulting from heteroepitaxy, leading to leakage currents and reduced device reliability, particularly when grown on silicon carbide substrates, where nucleation conditions such as temperature, V/III ratio, and thickness significantly impact dislocation densities and electrical properties.
Innovation Solution
A heterostructure with a stress controlling layer is fabricated, where the layer's attributes, such as thickness, vary laterally based on target stress variations in the semiconductor layer to modulate stresses and dislocation densities, thereby improving the reliability and efficiency of semiconductor devices like light emitting diodes and transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If heteroepitaxy is used to grow AlGaN layers on silicon carbide substrates, then device complexity and functionality are improved, but threading dislocations increase leading to leakage currents and reduced reliability
Solution Approach 1:
A stress controlling layer is introduced as an intermediary between the silicon carbide substrate and the AlGaN semiconductor layers. This intermediate layer mediates the lattice mismatch and thermal expansion differences, reducing threading dislocation densities while enabling the heteroepitaxial growth of high-quality AlGaN layers for advanced device functionality.
Solution Approach 2:
The stress controlling layer utilizes parameter changes in material properties (lattice constant, thermal expansion coefficient) to manage stress and dislocation formation. By selecting materials with specific parameter combinations and controlling layer thickness, the patent reduces dislocation densities while maintaining device performance.
2Ease of manufacture
If uniform stress controlling layer is used, then fabrication simplicity is improved, but inability to control lateral stress variations limits device performance optimization
Solution Approach 1:
The stress controlling layer transitions from uniform to laterally varying thickness or composition to provide local quality control. Different regions of the layer have different thicknesses or material compositions, enabling localized stress control in specific device regions while maintaining overall fabrication feasibility through established epitaxial techniques.
Solution Approach 2:
The stress controlling layer introduces dynamic stress control capability, where the stress state can be varied laterally to match different device requirements. This dynamic approach allows optimization of stress conditions for different functional regions of the semiconductor device.
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 stress controlling layer effectively reduces dislocation densities and modulates piezo-induced polarization fields, enhancing the electrical and structural properties of semiconductor devices, leading to improved reliability and efficiency.
Implementation Method 1
the fabricating the stress controlling layer includes varying at least one attribute of the stress controlling layer as a function of a lateral position based on a target variation of stresses in the semiconductor layer
Implementation Method 2
The stress controlling layer can include one or more attributes varies as a function of a lateral position based on a target variation of stresses in a semiconductor layer located directly under the stress controlling layer
Data Source
AI summary
A solution for fabricating a device is described. The solution can include fabricating a heterostructure for the device, which includes at least one stress controlling layer. The stress controlling layer can include one or more attributes varies as a function of a lateral position based on a target variation of stresses in a semiconductor layer located directly under the stress controlling layer. Embodiments are further directed to a heterostructure including at least one stress controlling layer and a device including the heterostructure.