UV Light Emitting Device Mesa Structure Current Crowding
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Solution Overview
Problem
Flip-chip type UV light emitting devices experience current crowding due to low electrical conductivity in n-type semiconductor layers, leading to insufficient light emission and reliability issues, necessitating improved current spreading and reduced forward voltage.
Innovation Solution
The UV light emitting device incorporates a substrate with a mesa structure having indentations, a passivation layer with openings, and bump electrodes that cover the passivation layer and partially overlap the mesa, allowing for uniform current distribution and reduced resistance, thereby preventing current crowding and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a flip-chip type structure is used to improve heat dissipation and luminous efficacy, then heat dissipation efficiency is improved, but current crowding occurs due to low electrical conductivity in n-type semiconductor layers
Solution Approach 1:
The patent divides the contact electrode into multiple segments (first contact electrode and second contact electrode) that contact different regions of the n-type semiconductor layer. This segmentation distributes the current injection points across multiple locations, preventing current crowding at any single point while maintaining the flip-chip structure's heat dissipation advantages.
2Illumination intensity
If current is increased to compensate for current crowding, then luminous intensity may be maintained, but forward voltage increases and reliability deteriorates
Solution Approach 1:
The patent applies different contact configurations to different regions of the semiconductor device. The first contact electrode contacts the n-type semiconductor layer at a first location while the second contact electrode contacts at a second location, creating localized current injection paths that optimize current distribution without requiring overall current increase, thus maintaining reliability.
3Reliability
If the n-type semiconductor layer is made thinner to reduce resistance, then electrical conductivity is improved, but mechanical strength and reliability are compromised
Solution Approach 1:
Instead of reducing the thickness (one dimension) of the n-type semiconductor layer to improve conductivity, the patent introduces a new dimension by adding multiple contact electrodes at different spatial locations. This multi-dimensional approach to current distribution improves electrical conductivity without compromising the mechanical integrity of the semiconductor layer.
Data Source
AI summary
A light emitting device including a substrate, a first semiconductor layer disposed on the substrate, a mesa including a second semiconductor layer and an active layer disposed on the first semiconductor layer, a first contact electrode contacting the first semiconductor layer, a second contact electrode contacting the second semiconductor layer, a passivation layer covering the first contact electrode, the mesa, and the second contact electrode, and including a first opening disposed on the first contact electrode and a second opening disposed on the second contact electrode, and first and second bump electrodes electrically connected to the first and second contact electrodes through the first and second openings, respectively, in which the first and second bump electrodes are disposed on the mesa, the passivation layer is disposed between the first bump electrode and the second contact electrode, and the first contact electrode includes an alloy layer.