Group III Nitride Epitaxy via Patterned Substrate Notches
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Solution Overview
Problem
The high dislocation density in Group III nitride films grown via heteroepitaxy on substrates like sapphire, silicon carbide, and silicon leads to defects, reducing charge carrier lifetime and thermal conductivity, and increasing threshold voltage in semiconductor elements.
Innovation Solution
A method involving the formation of notches with stepping structures on the epitaxial substrate, where the Group III nitride is grown using epitaxy, promoting lateral growth to restrict vertical growth and reduce dislocation density, utilizing chemical vapor or physical vapor deposition processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heteroepitaxy is used to grow Group III nitride on sapphire, silicon carbide, or silicon substrates, then the production cost is reduced compared to bulk material, but the dislocation density increases significantly due to lattice constant and thermal expansion coefficient differences
Solution Approach 1:
The substrate surface is segmented into multiple isolated island regions through patterning, where each island serves as an independent growth nucleus. This segmentation allows controlled epitaxial growth on each island while minimizing the propagation of dislocations across the entire substrate surface, thereby reducing overall dislocation density while maintaining cost-effective heteroepitaxy.
Solution Approach 2:
Different regions of the substrate are given different properties through selective patterning. The patterned regions have controlled geometry and spacing that promote high-quality crystal growth with reduced dislocations, while non-patterned regions can be optimized for other functions. This local differentiation allows simultaneous optimization of both manufacturing cost and crystal quality.
2Device complexity
If conventional heteroepitaxy is used without patterned substrates, then the fabrication process is simpler, but the threading dislocation density and stacking faults increase, reducing charge carrier lifetime and thermal conductivity
Solution Approach 1:
The substrate surface is pre-patterned with isolated island structures before the epitaxial growth of Group III nitride. This preliminary patterning action creates controlled nucleation sites that guide the subsequent crystal growth, ensuring that dislocations are confined to specific regions and do not propagate throughout the entire film, thereby improving charge carrier lifetime without significantly complicating the overall fabrication process.
3Productivity
If the Group III nitride film is grown to reduce dislocation density, then the luminous efficiency improves, but the threshold voltage increases and thermal conductivity decreases due to inherent imperfections
Solution Approach 1:
The inherent lattice mismatch and thermal expansion differences between the substrate and Group III nitride, which normally cause dislocations and reduce efficiency, are converted into a benefit through patterned substrate design. The patterned structure confines dislocations to specific regions, transforming what would be widespread defects into localized features that do not significantly impact overall device performance, thereby maintaining high luminous efficiency while managing threshold voltage and thermal conductivity.
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 minimizes dislocation density, enhancing the quality of the Group III nitride film, leading to improved luminous efficiency and reduced defects in light emitting diodes.
Implementation Method 1
The Group III nitride is grown on the epitaxial substrate via epitaxy process. Wherein, the Group III nitride growing at an upper portion of the epitaxial substrate restricts the vertical growth of the Group III nitride growing at the lower portion of the epitaxial substrate
Implementation Method 2
The Group III nitride is grown on the epitaxial substrate via epitaxy process. Wherein, the Group III nitride growing at an upper portion of the epitaxial substrate restricts the vertical growth of the Group III nitride growing at the lower portion of the epitaxial substrate
Implementation Method 3
The Group III nitride is grown on the epitaxial substrate via epitaxy process
Data Source
AI summary
A method for growing Group III nitride is provided, which includes the following steps. A plurality of notches separated from each other are formed at the epitaxial substrate surface via the pattering process. The plurality of notches each has at least one stepping structure with a predetermined inclination angle, wherein the stepping structure in each notch gradually descends towards the center of the corresponding notch. The Group III nitride is grown on the epitaxial substrate via epitaxy process. Wherein, the Group III nitride growing at an upper portion of the epitaxial substrate restricts the vertical growth of the Group III nitride growing at the lower portion of the epitaxial substrate, and the Group III nitride growing at the lower portion of the epitaxial substrate promotes the lateral growth of the Group III nitride growing at the upper portion of the epitaxial substrate.