Semiconductor Light Emitting Device Surface Texturing
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Solution Overview
Problem
Current semiconductor light emitting devices face challenges in achieving high external light extraction efficiency due to total reflection of light within the device, limiting their ability to emit light externally.
Innovation Solution
A method involving mesa-etching and dry etching techniques to create uneven portions on the surface of the first conductivity-type semiconductor layer, allowing for improved light extraction by varying the etching times based on grain boundaries in the conductive layer, and using a passivation layer to prevent electrical short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flat surface structure is used in semiconductor light emitting devices, then the manufacturing process is simple, but light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The patent applies curvature by forming uneven portions (protrusions and recesses) on the surface of the semiconductor layer. This curved/uneven surface structure modifies light extraction by changing the incident angles of internally reflected light, allowing more light to escape at angles that avoid total internal reflection. The uneven surface acts as a light extraction enhancement structure that maintains manufacturing feasibility while significantly improving light output efficiency.
2Loss of energy
If dry etching is performed to create uneven portions on the semiconductor layer surface, then light extraction efficiency is improved, but the fabrication process complexity increases
Solution Approach 1:
The patent uses a conductive layer as an intermediary material deposited on the semiconductor layer before etching. This conductive layer serves multiple functions: it protects the semiconductor layer during processing, controls the etching pattern formation, and enables the creation of uniform uneven portions through selective etching. The intermediary layer simplifies the overall process by providing a controlled mechanism to achieve the desired surface morphology without complex direct etching procedures.
Solution Approach 2:
The patent performs preliminary deposition of a conductive layer onto the semiconductor layer before etching. This preliminary action prepares the surface in a controlled manner, allowing subsequent etching to create uniform uneven portions. By pre-depositing the conductive layer, the process ensures consistent nucleation and growth patterns during etching, leading to reproducible light extraction enhancement without requiring complex in-situ process control.
3Shape
If the conductive layer is completely removed during etching, then uneven portions are formed on the semiconductor layer, but manufacturing precision control becomes more difficult
Solution Approach 1:
The patent applies local quality by creating uneven portions with specific protrusions and recesses at localized regions of the semiconductor layer surface. The etching process is controlled to form uneven portions with specific dimensional characteristics (protrusion height, recess depth, spacing) that are optimized for light extraction. Different regions may have different uneven portion densities or dimensions, allowing tailored light extraction properties in different areas of the device while maintaining overall process control through parameters like etching time, power, and gas flow.
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 enhances light extraction efficiency by 2% or more, enabling more effective external emission of light generated in the active layer, while preventing electrical short circuits and simplifying the fabrication process.
Implementation Method 1
The conductive layer is dry etched such that an upper surface of the first conductivity-type semiconductor layer is partially etched to have uneven portions thereon
Implementation Method 2
different areas of the upper surface of the first conductivity-type semiconductor layer are selectively exposed for different periods of time to the dry etching process due to a difference in etching ratios between grains and grain boundaries forming the conductive layer
Implementation Method 3
The second conductivity-type semiconductor layer and the active layer are mesa-etched to expose a portion of the first conductivity-type semiconductor layer
Implementation Method 4
forming a passivation layer to cover a lateral surface of a mesa structure exposed by the mesa-etching, prior to the forming of the conductive layer
Data Source
AI summary
A method of manufacturing a semiconductor light emitting device is performed on a light emitting structure including a sequential stack of a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer. The second conductivity-type semiconductor layer and the active layer are mesa-etched to expose a portion of the first conductivity-type semiconductor layer therethrough. A conductive layer is formed on the second conductivity-type semiconductor layer and the portion of the first conductivity-type semiconductor layer exposed by mesa-etching. In turn, the conductive layer is dry etched such that an upper surface of the first conductivity-type semiconductor layer is partially etched to have uneven portions formed thereon. The resulting semiconductor light emitting device has improved external light extraction efficiency while being easily manufactured.