Wider Single-Crystal Active Zone for Green Microwire LEDs
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Solution Overview
Problem
Lattice mismatch between semiconductor compounds in three-dimensional nanowire or microwire optoelectronic devices leads to structural defects and degradation of electronic and optical properties, limiting the production of light-emitting diodes with high emission wavelengths and large active zones.
Innovation Solution
The optoelectronic device features a wider single-crystal active zone made from a second semiconductor compound, such as InGaN, with a higher atomic proportion of an additional element, which is grown on top of a first doped portion like GaN, limiting lattice mismatch and mechanical stresses, allowing for thicker and more efficient quantum wells with improved internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active zone is made from a semiconductor compound different from the first doped portion (e.g., InGaN on GaN), then the emission wavelength can be extended to green spectrum and internal quantum efficiency is improved, but lattice mismatch occurs leading to structural defects and degradation of electronic properties
Solution Approach 1:
A wider single-crystal portion is introduced as an intermediary layer between the GaN first doped portion and the InGaN active zone. This intermediary layer has a diameter greater than the first doped portion, creating a gradual transition that reduces lattice mismatch and mechanical stresses, thereby preventing structural defects while enabling green spectrum emission with high internal quantum efficiency
Solution Approach 2:
The diameter parameter of the semiconductor structure is changed by introducing a wider single-crystal portion. This parameter change (increased diameter) serves to reduce the lattice mismatch between different semiconductor compounds, allowing the active zone to achieve higher indium content and thicker quantum wells without generating structural defects
2Illumination intensity
If the atomic proportion of additional element (e.g., indium) in the active zone is increased to achieve green emission, then emission wavelength is extended to green spectrum, but lattice mismatch increases leading to structural defects
Solution Approach 1:
The wider single-crystal portion acts as a mediator that enables higher indium content in the active zone. By providing a gradual transition zone, it allows the atomic proportion of indium to be increased to achieve green emission (wavelength extension) without directly interfacing with the GaN layer, thus preventing lattice mismatch-related structural defects
Solution Approach 2:
The atomic proportion of indium in the active zone is increased to extend emission wavelength to green spectrum. Simultaneously, the diameter parameter is changed by introducing a wider single-crystal portion, which compensates for the increased lattice mismatch caused by higher indium content, thereby preventing structural defects
3Reliability
If the thickness of quantum wells in the active zone is increased to improve luminous efficiency, then internal quantum efficiency is improved, but lattice mismatch leads to structural defects and degradation of electronic properties
Solution Approach 1:
The wider single-crystal portion serves as an intermediary that enables quantum wells of larger thickness to be formed. This intermediate layer reduces the lattice mismatch at the interface, allowing thicker quantum wells to be grown without generating structural defects, thereby achieving high internal quantum efficiency while maintaining manufacturing precision
Solution Approach 2:
The thickness parameter of quantum wells is increased to improve internal quantum efficiency and luminous efficiency. Simultaneously, the diameter parameter is changed by introducing a wider single-crystal portion, which reduces lattice mismatch and prevents structural defects that would otherwise occur with thicker quantum wells
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 configuration enhances the internal quantum efficiency and allows for larger thickness and higher atomic proportion of the additional element in quantum wells, enabling light emission in the green spectrum with improved luminous efficiency while minimizing structural defects.
Implementation Method 1
lattice mismatch between the semiconductor compound forming the active zone and that forming the first doped portion
Data Source
AI summary
The invention relates to an optoelectronic device, having at least one microwire or nanowire extending along a longitudinal axis substantially orthogonal to a plane of a substrate, and including: a first doped portion produced from a first semiconductor compound; an active zone extending from the first doped portion; a second doped portion, at least partially covering the active zone; characterised in that the active zone comprises a wider single-crystal portion: formed of a single crystal of a second semiconductor compound and at least one additional element; extending from an upper face of one end of the first doped portion, and having a mean diameter greater than that of the first doped portion.