Randomized Nanoporous GaN DBR Broadband Reflection
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Solution Overview
Problem
Existing periodic Distributed Bragg Reflectors (DBRs) have limited stop-band width due to refractive index contrast, which restricts their application in optoelectronic and photonic devices, and require complex growth conditions for strain-compensated ternary DBR structures.
Innovation Solution
The development of broadband omnidirectional DBRs using randomized thicknesses of lattice-matched nanoporous GaN and GaN layers, formed through electrochemical porosification and metal-organic chemical vapor deposition, introducing sufficient refractive index contrast and disorder to enhance stop-band width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If periodic DBR structure with alternating layers of different refractive indices is used, then reflectivity is achieved, but stop-band width is limited
Solution Approach 1:
The patent introduces randomness in the thickness of alternating layers, breaking the periodic symmetry. This asymmetry in layer thicknesses creates multiple reflection paths with different optical path lengths, which broadens the stop-band width beyond what is achievable with uniform periodic structures.
Solution Approach 2:
The patent changes the parameter of layer thickness from constant (periodic) to randomized values. By varying the thickness parameter randomly while maintaining lattice matching, the structure achieves broader spectral reflection without requiring extreme refractive index contrasts.
2Area of stationary object
If strain-compensated ternary DBR structures are used to increase refractive index contrast, then reflectivity improves, but growth conditions become complex
Solution Approach 1:
The patent employs nanoporous GaN layers instead of complex ternary compounds. The porous structure provides adjustable refractive index (lower than solid GaN) through controlled porosity, achieving the necessary index contrast without requiring strain-compensated ternary material systems and their complex growth conditions.
Solution Approach 2:
The patent changes the material state from solid to nanoporous, altering the refractive index parameter. This approach achieves the required optical contrast while maintaining compatibility with standard GaN growth processes, avoiding the complexity of ternary material growth.
3Area of stationary object
If randomized thicknesses of layers are introduced, then stop-band width increases, but manufacturing precision requirements change
Solution Approach 1:
The patent transitions from static uniform layer thickness to dynamic randomized thickness distribution. The randomness is intentionally introduced within controlled bounds, allowing the system to achieve broadband reflection while maintaining manufacturability through defined thickness variation ranges rather than requiring extreme precision.
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 significantly enhances the stop-band width by a factor of 2-3 compared to periodic DBRs, achieving broad reflectivity across UV to IR wavelengths with improved light-extraction efficiency and omnidirectional reflection, suitable for various optoelectronic and photonic applications.
Implementation Method 1
The metal-organic chemical vapor deposition can be used to grow the stack of doped/unintentionally doped or lightly doped III-nitrides
Implementation Method 2
followed by electrochemical porosification
Implementation Method 3
The DBRs are formed by electrochemical etching through sidewalls of mesa structures
Implementation Method 4
The DBRs are formed by electrochemical etching through defect-selective etching on planar structures
Implementation Method 5
Distributed Bragg Reflectors (DBRs) are the key building blocks for various optoelectronic and photonics applications
Implementation Method 6
By applying a degree of disorder to a fully periodic DBR, Anderson localization of light in a disordered media can be observed
Data Source
AI summary
A method of forming and a random Distributed Bragg Reflector (DBR) is disclosed. The random DBR includes a substrate and a plurality of alternating layers of lattice-matched nanoporous GaN (NP-GaN) and GaN formed on a top surface of the substrate, wherein at least one of the alternating layers has a thickness of λ/4n and an adjacent one of the alternating layers does not have a thickness of λ/4n, wherein λ is a wavelength of incident radiation and n is the refractive index of a particular layer of the plurality of alternating layers.