Light Emitting Element Protrusion Adhesion
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Solution Overview
Problem
Light emitting elements with nitride-based semiconductors face issues with current crowding due to lower electrical conductivity in p-type semiconductor layers, leading to electrostatic discharge, current leakage, and efficiency drooping, and existing techniques for current spreading are limited by defects in electrode adhesion and light absorption.
Innovation Solution
A light emitting element structure featuring a mesa with a current blocking layer, a transparent electrode, and an insulation layer, along with specific electrode configurations, including protrusions and grooves, to enhance current spreading and prevent electrostatic discharge, while improving adhesion and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a current blocking layer and transparent electrode are formed on the p-type semiconductor layer to spread electric current, then current spreading efficiency is improved, but electrode adhesion defects occur causing wire disconnection and peeling
Solution Approach 1:
An adhesion layer comprising Ti and Pt is introduced as an intermediary between the transparent electrode (ITO) and the p-type semiconductor layer. The Ti layer forms a diffusion barrier and chemical bond with the semiconductor, while the Pt layer provides mechanical strength and wire bondability, thus mediating the adhesion between electrode and substrate to prevent peeling and disconnection
Solution Approach 2:
The electrode structure uses a composite material approach by stacking multiple materials with different functions: ITO (transparent conductive oxide) for transparency and conductivity, Ti (transition metal) for adhesion and diffusion barrier, and Pt (precious metal) for mechanical strength and wire bonding. This composite structure optimizes both current spreading and adhesion reliability
2Ease of operation
If wire bonding is performed on the p-type electrode, then electrical connection is established, but poor adhesion causes wire disconnection and electrode peeling
Solution Approach 1:
The Pt layer serves as an intermediary that provides excellent wire bondability while maintaining strong adhesion to the underlying Ti layer and semiconductor. This intermediary layer enables reliable wire bonding operations without causing subsequent disconnection or peeling defects
Solution Approach 2:
The adhesion layer parameters are optimized with specific thickness ranges (Ti: 5-20 nm, Pt: 20-50 nm) to balance adhesion strength, wire bondability, and electrical conductivity. These parameter changes ensure reliable wire bonding while preventing adhesion failures
3Productivity
If existing electrode arrangements are used to spread current, then some current distribution is achieved, but light loss occurs due to absorption by electrodes
Solution Approach 1:
The current blocking layer is selectively positioned in specific regions where current concentration occurs, allowing current to spread uniformly in other regions. This local intervention optimizes current distribution while minimizing the total electrode area that absorbs light, thereby reducing light loss
Data Source
AI summary
A light-emitting element according to an embodiment of the present document has a transparent electrode having an opening, and the transparent electrode has a protrusion on a side surface of the opening. A second electrode pad is arranged on the opening of the transparent electrode, and abuts the protrusion. Accordingly, peeling of the second electrode pad can be prevented, thereby improving the reliability of the light-emitting element.