Light Emitting Device Capping Layer Thermal Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Light emitting devices face issues with ohmic characteristics and reliability due to separation between metal and semiconductor interfaces, leading to contact failures and delamination, particularly with indium tin oxide (ITO) and semiconductor layers.
Innovation Solution
A light emitting device design featuring a support substrate with a light emitting structure, grooves exposing the first semiconductor layer, and a capping layer with a material having a thermal expansion coefficient difference of 3 or less, along with an insulating layer and electrodes, improves ohmic characteristics and reliability by preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ITO is directly formed on the second semiconductor layer to improve ohmic characteristic, then the driving voltage is reduced, but the metal and semiconductor are easily separated at the interface
Solution Approach 1:
An insulating layer is introduced as an intermediary between the ITO electrode and the second semiconductor layer. This intermediate layer prevents direct contact between metal and semiconductor, eliminating the separation problem at the interface while maintaining electrical functionality through the insulating layer structure.
Solution Approach 2:
The electrode structure is transformed from a simple ITO-semiconductor interface to a composite structure comprising ITO, insulating layer, and semiconductor layer. This composite structure combines the advantages of ITO (low driving voltage, good ohmic characteristic) with the stability of the insulating layer, preventing interface separation.
2Reliability
If an insulating layer is formed to cover the ITO, then interface separation is prevented, but the insulating layer is lifted and contact failures occur
Solution Approach 1:
A buffer layer is introduced as an intermediary between the insulating layer and the second semiconductor layer. This buffer layer acts as a transition zone that prevents the insulating layer from lifting by distributing stress and improving adhesion, thereby maintaining contact reliability while preserving insulating layer stability.
Solution Approach 2:
The buffer layer is selectively positioned only where needed - between the insulating layer and the second semiconductor layer - to provide local reinforcement and prevent lifting. This localized approach maintains insulating layer stability without affecting overall device performance.
3Reliability
If a capping layer is formed on the ITO, then the structure is protected, but delamination occurs at the ITO-semiconductor interface
Solution Approach 1:
The insulating layer and buffer layer together form a multi-layer intermediary structure between the ITO and the second semiconductor layer. This intermediate structure prevents delamination by distributing thermal and mechanical stress, maintaining interface adhesion while providing the protective function of a capping layer.
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 enhances ohmic characteristics and driving voltage while preventing delamination and lifting at the interface, thereby improving the reliability of the light emitting device.
Implementation Method 1
a first layer having a material of which a difference in thermal expansion coefficient with the second semiconductor layer is 3 or less
Data Source
AI summary
An embodiment relates to a light emitting device comprise a second electrode which includes indium tin oxide (ITO), an ohmic characteristic between a second semiconductor layer and the second electrode is improved and a driving voltage is also improved. An embodiment relates to a light emitting device comprise a capping layer that can overlap the second semiconductor layer with the second electrode interposed therebetween and include a material of which a difference in thermal expansion coefficient with the second semiconductor layer is 3 or less. Therefore, since the capping layer is electrically connected to the second electrode, delamination and lifting of an interface between the second electrode and the second semiconductor layer is prevented, and reliability of the light emitting device is improved.