Semiconductor Light Emitting Device Electrode Structure
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Solution Overview
Problem
Semiconductor light emitting devices face challenges in minimizing light reflection or absorption, maximizing luminous efficiency with a large light emitting area, and achieving uniform current spreading while maintaining high reliability and enabling mass production.
Innovation Solution
A semiconductor light emitting device with a conductive substrate, a first conductivity type semiconductor layer, and a second conductivity type semiconductor layer, featuring a first electrode layer between the substrate and the first semiconductor layer, and a second electrode part with electrode pad units, extending units, and connecting units that are electrically insulated and separated to optimize light emission and current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large electrode area is used to ensure low contact resistance and uniform current spreading, then current distribution is improved, but the light emitting area is reduced and luminous efficiency decreases
Solution Approach 1:
The patent transitions from a planar electrode layout to a three-dimensional vertical structure. The electrode is divided into multiple layers (first electrode layer, second electrode layer, third electrode layer) stacked vertically, allowing current to spread through the thickness dimension rather than requiring large lateral area. This dimensional change enables uniform current distribution while preserving the light emitting area on the surface.
Solution Approach 2:
The electrode structure is segmented into multiple distinct layers: a first electrode layer in contact with the substrate, a second electrode layer, and a third electrode layer. Each layer serves specific functions for current injection and distribution. This segmentation allows the electrode to achieve uniform current spreading through distributed contact points across different depths, reducing the need for large lateral electrode area.
2Reliability
If electrodes are positioned to minimize contact resistance, then electrical connection is improved, but light absorption by electrodes increases and luminous efficiency decreases
Solution Approach 1:
The patent positions electrodes primarily in the vertical dimension rather than spreading them laterally across the light path. The first electrode layer contacts the substrate from below, and subsequent electrode layers are stacked vertically, minimizing the horizontal footprint of electrodes that would otherwise absorb light. This vertical arrangement maintains good electrical connection while reducing light absorption losses.
Solution Approach 2:
The patent introduces a reflective layer as an intermediary between the electrode and the active region. This reflective layer redirects light that might otherwise be absorbed by the electrode back toward the light emitting region, reducing energy loss while maintaining the electrode's electrical connection function.
3Ease of manufacture
If a vertical structure with substrate contact is used, then manufacturing is simplified, but light extraction efficiency is reduced due to substrate absorption
Solution Approach 1:
The patent introduces a reflective layer as an intermediary between the substrate and the active region. This reflective layer has high reflectivity for the emitted light wavelength, preventing the substrate from absorbing light and instead redirecting it back through the active region for extraction. This maintains the manufacturing simplicity of substrate contact while dramatically improving light extraction efficiency.
Solution Approach 2:
The patent converts the substrate's inherent light absorption property, which is normally harmful, into a beneficial configuration by adding a reflective layer. The substrate still provides mechanical support and electrical contact (maintaining ease of manufacture), but the reflective layer ensures that any light interacting with the substrate is reflected back rather than absorbed, turning a potential loss mechanism into a light extraction enhancement.
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 solution enhances luminous efficiency by minimizing light absorption, ensures uniform current spreading, and facilitates high-quality mass production with reduced manufacturing costs and increased reliability.
Implementation Method 1
The first electrode layer may reflect light generated from the active layer
Data Source
AI summary
There is provided a semiconductor light emitting device that minimizes reflection or absorption of emitted light, maximizes luminous efficiency with the maximum light emitting area, enables uniform current spreading with a small area electrode, and enables mass production with high reliability and high quality. A semiconductor light emitting device according to an aspect of the invention includes first and second conductivity type semiconductor layers, an active layer formed therebetween, first electrode layer, and a second electrode part electrically connecting the semiconductor layers. The second electrode part includes an electrode pad unit, an electrode extending unit, and an electrode connecting unit connecting the electrode pad unit and electrode extending unit.