Light-Emitting Structure With Dielectric Reflector for Heat and Light Loss
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Solution Overview
Problem
Conventional light-emitting devices face issues such as light absorption, current crowding, and poor heat dissipation due to the growth substrate, which affect their luminous brightness and efficiency, particularly in vertical type devices.
Innovation Solution
A light-emitting device design featuring a semiconductor epitaxial structure with a reflection layer and a light-transmissive dielectric structure, where the dielectric structure consists of sublayers with varying refractive indices to enhance light extraction efficiency, and a metal bonding layer for improved heat dissipation and current spreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal bonding layer is used to transfer the semiconductor epitaxial structure, then heat dissipation and current spreading are improved, but light absorption increases and light extraction efficiency decreases
Solution Approach 1:
A light-transmissive dielectric layer is introduced as an intermediary between the metal bonding layer and the semiconductor epitaxial structure. This dielectric layer has higher refractive index than both the metal bonding layer and the semiconductor epitaxial structure, serving as an optical mediator that reflects light back toward the light-exiting surface while allowing thermal and electrical functions to pass through to the metal bonding layer.
Solution Approach 2:
The patent employs a composite structure combining metal bonding layer and light-transmissive dielectric layer with specific refractive index relationships (n_dielectric > n金属 and n_dielectric > n半导体). This composite material system achieves both thermal management through the metal layer and light extraction enhancement through the dielectric layer's optical properties.
2Illumination intensity
If a conventional ODR is used to reflect light, then light that has incident angle greater than critical angle is reflected back, but light with incident angle smaller than critical angle is absorbed or requires multiple reflections
Solution Approach 1:
The patent changes the refractive index parameter of the dielectric layer to be higher than both the metal bonding layer and the semiconductor epitaxial structure. This parameter change enables the dielectric layer to act as an effective optical mirror through total internal reflection, improving light extraction efficiency for various incident angles.
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 design significantly improves light extraction efficiency and luminous brightness by minimizing light absorption and promoting efficient light reflection and emission, as demonstrated by optical reflectivity tests showing increased reflectivity and brightness compared to conventional devices.
Implementation Method 1
The light-transmissive dielectric structure includes a first sublayer made of a first material, a second sublayer made of a second material, and a third sublayer made of a third material that are sequentially disposed in the stacking direction. The first sublayer has a first refractive index (n1), the second sublayer has a second refractive index (n2), and the third sublayer has a third refractive index (n3), where n2>n1, n2>n3.
Implementation Method 2
The reflection layer is disposed on the semiconductor epitaxial structure away from the light-exiting surface, and is adapted for reflecting light emitted by the active layer.
Implementation Method 3
a metal bonding layer for improved heat dissipation and current spreading
Implementation Method 4
a metal bonding layer for improved heat dissipation and current spreading
Data Source
AI summary
A light-emitting device includes a semiconductor epitaxial structure, a reflection layer, and a light-transmissive dielectric structure. The semiconductor epitaxial structure has a first surface and a second surface, and includes a first semiconductor layer, an active layer, and a second semiconductor layer. The first surface is a light-exiting surface. The reflection layer is disposed on the semiconductor epitaxial structure away from the light-exiting surface, and is adapted for reflecting light emitted by the active layer. The light-transmissive dielectric structure is disposed between the reflection layer and the semiconductor epitaxial structure, and includes a first sublayer, a second sublayer, and a third sublayer. A light-emitting apparatus and a plant lighting apparatus are also provided.