LED Package Recess and Capping Layer for Atom Migration
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Solution Overview
Problem
Conventional light-emitting element packages with flip-chip bonding structures face reliability issues due to atom migration from the reflective layer, affecting the performance and longevity of the elements.
Innovation Solution
A light-emitting element design featuring a recess in the first conductive type semiconductor layer, a reflective layer spaced apart from the recess, and a capping layer with a transparent electrode to prevent atom migration, reduce thermal expansion coefficient differences, and enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a reflective layer is disposed close to the semiconductor layers to improve light reflection efficiency, then light extraction efficiency is improved, but atoms of the reflective layer migrate to the semiconductor layers causing reliability degradation
Solution Approach 1:
An insulating layer is introduced as an intermediary between the reflective layer and the semiconductor layers. This insulating layer prevents atom migration from the reflective layer to the semiconductor layers while maintaining the reflective layer's light reflection function, thus resolving the contradiction between light extraction efficiency and reliability
Solution Approach 2:
The structure is segmented by introducing a separate insulating layer that divides the space between the reflective layer and semiconductor layers. This segmentation isolates the reflective layer atoms from the semiconductor layers, preventing contamination while preserving optical performance
2Reliability
If the reflective layer is spaced apart from the recess to prevent atom migration, then reliability is improved, but light extraction efficiency decreases
Solution Approach 1:
The insulating layer serves as a mediator that allows the reflective layer to be spaced apart from the recess while maintaining effective light reflection. The insulating layer fills the gap and ensures continuous optical path, preventing both atom migration and light extraction efficiency loss
3Reliability
If a capping layer is disposed to surround the reflective layer to prevent atom migration, then reliability is improved, but device complexity increases
Solution Approach 1:
The insulating layer performs multiple functions simultaneously: it acts as a barrier to prevent atom migration, provides electrical insulation, and serves as a structural support. This multi-functionality improves reliability without proportionally increasing device 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
The solution improves the reliability and electrical properties of the light-emitting element by preventing atom migration, minimizing peeling phenomena, and increasing light extraction efficiency through the use of a transparent capping layer.
Implementation Method 1
a capping layer disposed on the reflective layer to surround the reflective layer
Implementation Method 2
atoms of a reflective layer disposed on a lower portion of a p-GaN layer are migrated to reflect light emitted from an active layer
Implementation Method 3
the capping layer is formed of a TCO instead of a metal material to transmit or reflect light so that light extraction efficiency can be improved
Implementation Method 4
the capping layer serves to spread a current so that electrical properties can be improved
Implementation Method 5
the capping layer is disposed to reduce the interval of thermal expansion coefficients between the reflective layer and periphery layers thereof
Data Source
AI summary
A light-emitting element according to an embodiment comprises: a light-emitting structure including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer formed between the first and second conductive type semiconductor layers; a reflective layer formed on the second conductive type semiconductor layer; a capping layer formed on the reflective layer to surround the reflective layer; a first electrode electrically connected with the first conductive type semiconductor layer; a first bonding pad electrically connected with the first electrode; and a second bonding pad electrically connected with the second electrode, wherein the light-emitting structure includes a recess extending to a region of the first conductive type semiconductor layer through the second conductive type semiconductor layer and the active layer; the first electrode is formed within the recess and electrically connected with the first conductive type semiconductor layer, and includes a region bent along a side surface of the second bonding pad; the reflective layer is formed to be spaced apart from the recess; and the capping layer includes a transparent electrode.