InGaN Layer Growth via Segmented Sublayers
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Solution Overview
Problem
III-V semiconductor layers, such as InGaN, face strain relaxation and resulting defects when grown heteroepitaxially beyond a critical thickness, leading to non-uniform indium composition and surface roughening, which deteriorates crystal quality and is detrimental for device production.
Innovation Solution
The method involves growing InGaN layers in multiple sublayers using different sets of growth conditions to maintain a constant indium incorporation rate, either by reducing the incoming flux or increasing the desorption flux of indium, thereby preventing strain relaxation and maintaining a uniform indium concentration across the layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If InGaN layers are grown heteroepitaxially beyond critical thickness to achieve sufficient layer thickness for device applications, then the layer thickness is improved, but strain relaxation occurs resulting in crystal defects and non-uniform indium composition
Solution Approach 1:
The InGaN layer is divided into multiple sublayers with different indium concentrations. Each sublayer is grown to a thickness below its critical thickness to prevent strain relaxation, while the cumulative thickness exceeds the critical thickness for device applications. This segmentation allows achieving both sufficient total thickness and high crystal quality without defects.
2Length of stationary object
If InGaN layers are grown heteroepitaxially beyond critical thickness to achieve sufficient layer thickness, then the layer thickness is improved, but surface roughening occurs deteriorating the surface quality
Solution Approach 1:
By segmenting the thick InGaN layer into multiple thin sublayers, each sublayer maintains a smooth surface morphology as it stays below the critical thickness for strain relaxation. The interfaces between sublayers are coherent and defect-free, resulting in an overall smooth surface even though the total thickness exceeds the critical thickness.
3Ease of manufacture
If constant growth conditions are used beyond critical thickness, then the growth process is simplified, but indium concentration becomes non-uniform across the layer thickness
Solution Approach 1:
Different indium concentrations are applied to different sublayers based on their position and thickness requirements. Each sublayer is grown with locally optimized conditions to achieve uniform indium incorporation within that sublayer, while the overall layer structure maintains composition control through the gradient design.
4Reliability
If InGaN layers are grown with high indium incorporation to achieve desired optical properties, then the optical performance is improved, but strain relaxation is promoted leading to increased defects
Solution Approach 1:
The indium concentration parameter is varied across different sublayers, with higher indium content in sublayers where optical performance is critical and lower indium content in sublayers where strain accumulation is a concern. This parameter change strategy allows optimizing optical properties while maintaining crystal quality through controlled composition gradients.
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 results in InGaN layers with a substantially uniform indium composition, reduced defects, and a smoother surface, making them more suitable for device fabrication by preventing strain relaxation and associated defects.
Implementation Method 1
The InGaN layer may initially grow 'pseudomorphically' to the underlying substrate, such that a lattice parameter of the InGaN layer is caused (e.g., forced by atomic forces) to substantially match a lattice parameter of the underlying substrate upon which it is grown.
Implementation Method 2
The lattice mismatch between the InGaN layer and the underling substrate (e.g., GaN) may induce strain in the crystal lattice of the InGaN layer, and this induced strain may increase with increasing thickness of the InGaN layer.
Implementation Method 3
InGaN layers may be deposited heteroepitaxially on an underlying substrate
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3B
AI summary
Embodiments of the invention relate to methods of fabricating semiconductor structures, and to semiconductor structures fabricated by such methods. In some embodiments, the methods may be used to fabricate semiconductor structures of III-V materials, such as InGaN. A semiconductor layer is fabricated by growing sublayers using differing sets of growth conditions to improve the homogeneity of the resulting layer, to improve a surface roughness of the resulting layer, and/or to enable the layer to be grown to an increased thickness without the onset of strain relaxation.