AlInGaN Growth Substrate Structure for Low V-Pit Epitaxy
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Solution Overview
Problem
Current methods for forming InGaN growth islands on substrates face challenges in achieving high indium content and lattice parameter matching for semiconductor optoelectronic structures, leading to defective structures with V-pits and limited relaxation, making it difficult to produce high-quality substrates for LEDs and other devices.
Innovation Solution
A process involving a donor substrate with a surface layer composed of alternations of InGaN primary and AlGaN secondary layers, where the indium and aluminum concentrations and thicknesses are selected to create a homogeneous AlInGaN layer with a natural lattice parameter different from the seed layer, allowing for thick, high-quality growth islands with reduced V-pit density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the indium content of the InGaN layer is increased to achieve higher lattice parameter for red/green LED emission, then the natural lattice parameter increases, but compressive strain increases leading to V-pits and dislocations
Solution Approach 1:
The InGaN surface layer is segmented into multiple thin sub-layers with varying indium concentrations (e.g., 5%, 10%, 15%, 20%) stacked in sequence. This segmentation allows the total indium content to be high (achieving desired lattice parameter) while each individual sub-layer remains thin enough to avoid V-pit formation, thus resolving the contradiction between lattice parameter matching and defect density
Solution Approach 2:
Different regions of the surface layer have different indium concentrations tailored to local requirements. The gradient structure provides locally optimized lattice parameters that gradually transition, reducing abrupt strain changes and minimizing dislocation formation while achieving the overall high lattice parameter needed for red/green LED emission
2Quantity of substance
If the thickness of the InGaN surface layer is increased to improve relaxation efficiency, then more indium can be incorporated, but V-pit density increases rapidly
Solution Approach 1:
The thick InGaN layer is divided into multiple thin sub-layers (e.g., several layers of 20-50 nm each). This segmentation enables the total indium content to be high while each sub-layer remains below the critical thickness for V-pit formation, thus allowing high indium content without proportional increase in V-pit density
Solution Approach 2:
The surface layer consists of periodic alternations of InGaN sub-layers with different indium concentrations. This periodic structure allows continuous incorporation of indium across multiple periods while each period maintains safe thickness, achieving high total indium content with controlled defect density
3Adaptability or versatility
If a homogeneous InGaN layer with high indium content is formed, then the lattice parameter can be tuned for different LED colors, but the layer becomes excessively strained and relaxes imperfectly
Solution Approach 1:
The surface layer has spatially varying indium concentrations arranged in a gradient or stepped pattern. This local quality variation allows different regions to have different lattice parameters adapted to specific LED color requirements, while the gradual transition between regions prevents excessive localized strain and improves overall relaxation quality
Solution Approach 2:
The indium concentration parameter is varied systematically across the layer structure (e.g., 5%, 10%, 15%, 20% in sequence). This parameter change strategy enables continuous tuning of the average lattice parameter for different LED applications while distributing strain more evenly, improving relaxation efficiency compared to a homogeneous high-indium layer
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 enables the formation of thick AlInGaN surface layers with a natural lattice parameter suitable for high indium content, reducing V-pit density and enabling the growth of islands with a freely selectable lattice parameter, improving crystal quality and relaxation efficiency.
Implementation Method 1
a heat treatment is applied to at least partially relax these islands
Implementation Method 2
heat treating the relaxation structure to at least partially relax the growth islands
Implementation Method 3
forming the surface layer as a plurality of alternations of an InGaN primary layer and of an AlGaN secondary layer
Data Source
AI summary
A process for fabricating a growth substrate comprises preparing a donor substrate by forming a crystalline semiconductor surface layer on a seed layer of a carrier. This preparation comprises forming the surface layer as a plurality of alternations of an InGaN primary layer and of an AlGaN secondary layer, the indium concentration and the thickness of the primary layers and the aluminum concentration and the thickness of the secondary layers being selected so that a homogeneous AlInGaN layer that is equivalent, in terms of concentration of aluminum and indium, to the surface layer has a natural lattice parameter different from the lattice parameter of the seed layer.