GaP Light Extraction Layer Roughening via Anisotropic Etching
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Solution Overview
Problem
Existing methods for surface roughening of GaP light extraction layers with {100} surfaces, especially those off-angled and rich in P, are inefficient and difficult to implement, limiting light extraction efficiency in light emitting devices due to challenges with chemical etching and the need for complex processing steps.
Innovation Solution
A method involving an etching solution with specific compositions of acetic acid, hydrofluoric acid, nitric acid, and iodine is used to efficiently form surface roughening projections on GaP light extraction layers with off-angled {100} surfaces, enabling anisotropic etching and improving light extraction efficiency without damaging the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching methods are used on GaP light extraction layers with off-angled {100} surfaces, then the etching process can be performed, but the etching efficiency is low and the process is difficult to implement
Solution Approach 1:
The patent changes the chemical composition parameters of the etching solution by specifying precise ratios of acetic acid (40-75%), hydrofluoric acid (2-8%), nitric acid (4.5-16%), and iodine (0.6-1.5%), with controlled water content (2-25%). This parameter optimization enables efficient anisotropic etching of GaP light extraction layers with off-angled {100} surfaces, resolving the contradiction between etching efficiency and process difficulty.
2Productivity
If the light extraction layer is made thicker to increase light extraction from side faces, then light extraction efficiency improves, but the fabrication process becomes more complex
Solution Approach 1:
The patent applies surface roughening treatment to the light extraction layer before device assembly and packaging. This preliminary action creates irregularities that enhance light extraction from side faces of thicker layers without requiring additional complex fabrication steps later, thus resolving the contradiction between improved light extraction efficiency and fabrication process complexity.
3Productivity
If the metal electrode area is reduced to improve light extraction efficiency, then light extraction improves, but current spreading becomes insufficient
Solution Approach 1:
The patent creates local quality variations by forming surface roughening projections only in specific regions of the light extraction layer. This localized roughening enhances light extraction in those areas without requiring reduction of the metal electrode area, thus resolving the contradiction between light extraction efficiency and current spreading reliability.
4Productivity
If surface roughening is applied to main and side faces of light extraction layers, then light extraction efficiency significantly improves, but additional processing steps are required
Solution Approach 1:
The patent develops a universal etching solution that effectively roughens both the main face and side faces of GaP light extraction layers with off-angled {100} surfaces using a single processing step. This multi-functional etching approach eliminates the need for separate roughening processes for different surfaces, resolving the contradiction between improved light extraction efficiency and increased processing steps.
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
The method allows for effective surface roughening of both the main and side faces of GaP light extraction layers, significantly enhancing light extraction efficiency and simplifying the fabrication process by enabling efficient formation of irregularities on previously difficult-to-reach areas.
Implementation Method 1
enabling anisotropic etching and improving light extraction efficiency without damaging the electrode
Data Source
AI summary
A light emitting device wafer is fabricated, having a light emitting layer section, composed of AlGaInP, based on a double heterostructure and a GaP light extraction layer disposed on the light emitting layer portion, having a first main surface thereof appearing on the first main surface of the wafer, so as that a P-rich off-angled {100} surface, having a higher existence rate of P atoms than an exact {100} surface, appears on the first main surface the GaP light extraction layer. The main first surface of the GaP light extraction layer is etched with an etching solution FEA so as to form surface roughening projections. Therefore, it provides a method of fabricating a light emitting device capable of applying surface roughening easily to the GaP light extraction surface having the {100} surface, off-angled to be P-rich, as a main surface thereof.