GaN Light Extraction via In-Situ Gallium Reflection Layer
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Solution Overview
Problem
Conventional light-emitting semiconductor devices face inefficiencies due to total internal reflection of light, which is absorbed as heat, and require costly and time-consuming etching processes for light extraction, often involving ex-situ growth interruptions.
Innovation Solution
Incorporating a light-reflection layer between epitaxial semiconductor layers, utilizing gallium or other reflective materials with different refractive indices, formed during uninterrupted epitaxial growth using processes like MOCVD or MBE, to facilitate light extraction by reflecting light out of the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional light-emitting semiconductor devices are used, then light is produced by the active layer, but total internal reflection causes light to be absorbed as heat, reducing light extraction efficiency
Solution Approach 1:
A light reflection layer comprising a group III material (such as gallium) is introduced as an intermediary between the first semiconductor layer and the second semiconductor layer containing the active layer. This intermediate layer reflects light that would otherwise be absorbed, redirecting it to emerge from the device and converting a harmful effect (light absorption) into a beneficial one (light extraction).
Solution Approach 2:
The refractive index parameter is utilized to solve the light extraction problem. The light reflection layer has a different refractive index compared to the surrounding semiconductor layers, creating optical conditions that favor light reflection and extraction. By controlling the refractive index mismatch, the device optimizes light emergence while minimizing energy loss as heat.
2Loss of energy
If etching processes are used for light extraction, then light can be extracted from the device, but the process is costly and time-consuming, involving growth interruptions
Solution Approach 1:
The light reflection layer is formed during the epitaxial growth process itself, before the completion of the semiconductor device structure. By incorporating the light extraction functionality into the growth stage through preliminary formation of the group III material layer, the need for subsequent time-consuming etching operations is eliminated, and growth interruptions are avoided.
Solution Approach 2:
The formation of the light reflection layer is merged with the epitaxial growth process. The group III material layer is deposited and then selectively removed in-situ during the same growth run, combining multiple functions (light extraction structure formation and growth continuation) into a single uninterrupted process, thereby eliminating time losses associated with separate etching steps.
3Loss of energy
If etching processes are used for light extraction, then light can be extracted from the device, but the process complexity increases with ex-situ growth interruptions
Solution Approach 1:
The group III material layer serves as a temporary intermediary structure that simplifies the overall fabrication process. Instead of requiring complex ex-situ etching operations, this intermediate layer provides a straightforward in-situ method for achieving light extraction, reducing fabrication process complexity while maintaining effective light extraction.
4Loss of energy
If a light-reflection layer with different refractive index is incorporated, then light extraction is enhanced, but the device structure becomes more complex
Solution Approach 1:
Rather than adding complex structural elements, the solution changes the refractive index parameter by introducing a light reflection layer with different optical properties. This parameter-based approach enhances light extraction efficiency while maintaining relative structural simplicity, as the enhancement comes from material property selection rather than geometric complexity.
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
Enhances light extraction efficiency by allowing light to emerge from the device without absorption as heat, eliminating the need for complex etching processes and growth interruptions, thereby improving device performance and reducing costs.
Implementation Method 1
a light-reflection layer configured to cause at least a portion of light produced by the active layer to emerge from the semiconductor device via a surface of the second semiconductor layer
Implementation Method 2
The semiconductor material has a first refractive index. The light-reflection layer may include a reflective material having a second refractive index. The second refractive index may be different from the first refractive index.
Data Source
AI summary
Aspects of the disclosure provide for mechanisms for fabricating light extraction structures for semiconductor devices (e.g., light-emitting devices). In accordance with some embodiments, a semiconductor device is provided. The semiconductor device may include: a first semiconductor layer including an epitaxial layer of a semiconductor material; a second semiconductor layer comprising an active layer; and a light-reflection layer configured to cause at least a portion of light produced by the active layer to emerge from the semiconductor device via a surface of the second semiconductor layer, wherein the light-reflection layer is positioned between the first semiconductor layer and the second semiconductor layer. In some embodiments, the semiconductor material includes gallium nitride. In some embodiments, the light-reflection layer includes a layer of gallium.