Vertical LED Groove Under First Conductivity Layer
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Solution Overview
Problem
Vertical type light emitting diodes face challenges in achieving uniform current spreading and preventing light loss due to cathode pads and electrode extensions, which also risk damage during manufacturing processes like wet etching, affecting production yield and efficiency.
Innovation Solution
The design incorporates a groove in the mesa structure with a specific shape to expose the first conductivity type semiconductor layer, along with a combination of first and second contact portions in the electrodes, and an upper electrode pad positioned to minimize light absorption, allowing for improved current spreading and light extraction while protecting the semiconductor layers during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cathode pad and electrode extension are disposed on epitaxial layer to assist current spreading, then current spreading performance is improved, but light emission is blocked and luminous efficacy deteriorates
Solution Approach 1:
The electrode extension is moved from the upper surface of the epitaxial layer to the lower surface, changing its spatial dimension. This allows the electrode to provide current spreading assistance without blocking light emission from the upper surface, resolving the contradiction between current spreading performance and luminous efficacy
Solution Approach 2:
A groove structure is introduced as an intermediary element to expose the lower surface of the epitaxial layer. This groove enables the electrode extension to contact the epitaxial layer from below while maintaining light emission pathways from above, mediating between current spreading requirements and light extraction efficiency
2Loss of energy
If wet etching is used to roughen epitaxial layer surface for improved light extraction, then light extraction efficiency is improved, but bonding metal layer or reflective metal layer is damaged and production yield decreases
Solution Approach 1:
The groove structure provides localized exposure of the epitaxial layer lower surface only in specific regions, allowing selective roughening or treatment without exposing the metal layers to etchants across the entire structure. This localized approach maintains light extraction efficiency while protecting the metal layers from damage
Solution Approach 2:
The groove acts as a protected pathway that allows etching or surface treatment to reach the epitaxial layer lower surface without directly exposing the metal layers to etchants. This intermediary structure enables the beneficial surface treatment while preventing harmful exposure of sensitive metal layers
Data Source
AI summary
A light emitting diode includes: a first conductivity type semiconductor layer; a mesa including an active layer and a second conductivity type semiconductor layer, the mesa having a groove disposed under some region of the first conductivity type semiconductor layer to expose an edge of the first conductivity type semiconductor layer, the groove exposing the first conductivity type semiconductor layer; a first electrode including a first contact portion electrically connected to the first conductivity type semiconductor layer through the groove; a second electrode disposed between the first electrode and the second conductivity type semiconductor layer and electrically connected to the second conductivity type semiconductor layer; and an upper electrode pad disposed adjacent to the first conductivity type semiconductor layer and connected to the second electrode, wherein the groove has a shape surrounding a region including a center of the mesa and partially open.