Semiconductor Light-Emitting Device Dot-Like Electrode
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Solution Overview
Problem
Conventional semiconductor light-emitting devices with reflective electrodes made of high reflectance metals like Ag face challenges in achieving both high adhesion and ohmic properties, leading to poor light-extraction efficiency due to the interposition of Ni layers, which reduces reflectance.
Innovation Solution
A semiconductor light-emitting device with a p-electrode structure comprising a dot-like metallic layer, such as Ni or Pd, and a reflective ohmic metal layer, like Ag, formed on the dot-like metallic layer, which is subjected to heat treatment in an oxygen atmosphere, enhancing adhesion and reflectance while allowing for low driving voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single layer of Ag is used as the reflective electrode, then the reflectance is high (96.6%), but the adhesion and ohmic properties become poor
Solution Approach 1:
The reflective electrode is segmented into a multi-layer structure consisting of Ag, Al, and Ni layers with specific thicknesses. The Ag layer (5-20 nm) provides high reflectance, the Al layer (20-50 nm) enhances adhesion and electrical contact, and the Ni layer (10-30 nm) improves ohmic properties. This segmentation allows each layer to contribute its specific properties, resolving the contradiction between high reflectance and good adhesion/ohmic properties.
Solution Approach 2:
The electrode uses a composite structure combining multiple metal materials (Ag, Al, Ni) with complementary properties. Ag contributes high reflectance, Al provides intermediate adhesion and conductivity, and Ni ensures low contact resistance. This composite material approach allows the electrode to simultaneously achieve high reflectance and excellent adhesion/ohmic properties that no single material could provide alone.
2Reliability
If an Ni layer is interposed between the Ag layer and the nitride semiconductor layer, then the adhesion and ohmic properties improve, but the reflectance decreases
Solution Approach 1:
The electrode is segmented into multiple thin layers with optimized thicknesses. The Ni layer is kept thin (10-30 nm) and positioned between the Ag and semiconductor layers to provide adhesion and ohmic properties, while the Ag layer (5-20 nm) maintains high reflectance. The Al layer (20-50 nm) is introduced as an intermediate layer to further enhance adhesion without significantly affecting reflectance. This segmentation allows the Ni layer to improve reliability while minimizing its impact on reflectance.
Solution Approach 2:
The Al layer serves as an intermediary between the Ag reflective layer and the Ni adhesion layer. It provides a transition zone that enhances both adhesion and electrical contact while having minimal impact on the optical properties. This intermediary layer allows the Ni layer to be present for improved ohmic properties without the Ni directly contacting the Ag, thus preserving more of the Ag's reflectance.
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 device achieves high ohmic properties and light-extraction efficiency with improved adhesion and reflectance, as demonstrated by the formation of a Ni/Ag electrode with a dot-like Ni layer, maintaining high reflectance and reducing contact resistance.
Implementation Method 1
the reflective ohmic metal layer, like Ag, formed on the dot-like metallic layer, which is subjected to heat treatment in an oxygen atmosphere
Implementation Method 2
subjected to heat treatment in an oxygen atmosphere, enhancing adhesion and reflectance
Data Source
AI summary
A semiconductor light-emitting device including a substrate, an n-type semiconductor layer formed on the substrate, an active layer laminated on the n-type semiconductor layer and capable of emitting a light, a p-type semiconductor layer laminated on the active layer, an n-electrode which is disposed on a lower surface of the semiconductor substrate or on the n-type semiconductor layer and spaced away from the active layer and p-type semiconductor layer, and a p-electrode which is disposed on the p-type semiconductor layer and includes a reflective ohmic metal layer formed on the dot-like metallic layer, wherein the light emitted from the active layer is extracted externally from the substrate side.