LED Mesa Structure Insulation for Humidity Reliability
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Solution Overview
Problem
Light emitting diodes (LEDs) face reduced light output due to protective layers that absorb light, while also being vulnerable to moisture, which compromises their reliability under high humidity conditions.
Innovation Solution
A light emitting diode design that includes a mesa structure with an exposed n-type semiconductor layer and a first insulation layer partially covering the p-type semiconductor layer, reducing the need for a protective layer and preventing metal migration, thereby enhancing reliability and light output under high humidity conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is added to prevent moisture damage, then reliability under high humidity conditions is improved, but light output is reduced due to light absorption
Solution Approach 1:
The protective function is segmented into two parts: (1) a mesa structure that exposes the n-type semiconductor layer to provide a physical barrier against moisture, and (2) a first insulation layer that provides additional electrical insulation and moisture protection. This segmentation allows the device to achieve reliability protection without requiring a comprehensive protective layer that would block light.
Solution Approach 2:
The insulation properties are applied locally rather than uniformly across the entire device. The first insulation layer is disposed between the exposed n-type semiconductor layer and the second bonding pad, providing protection only in the specific region where electrical insulation is needed, rather than covering the entire light-emitting surface with a light-absorbing protective layer.
2Reliability
If a protective layer is added to prevent moisture damage, then reliability under high humidity conditions is improved, but device complexity increases
Solution Approach 1:
The first insulation layer serves multiple functions simultaneously: (1) providing electrical insulation between the exposed n-type semiconductor layer and the second bonding pad, (2) preventing moisture ingress to the semiconductor layers, and (3) maintaining structural integrity. This multi-functionality eliminates the need for separate protective layers, reducing device complexity while improving reliability.
3Illumination intensity
If the n-type semiconductor layer is exposed by the mesa structure, then light output is improved by removing light-absorbing materials, but vulnerability to moisture increases
Solution Approach 1:
The first insulation layer acts as a thin film barrier that protects the exposed n-type semiconductor layer from moisture ingress. This thin film approach provides effective moisture protection without adding significant structural complexity or requiring thick protective layers that would interfere with light output.
Data Source
AI summary
A light emitting diode including an n-type semiconductor layer, a mesa disposed on the n-type semiconductor layer and exposing a portion thereof, and including an active layer and a p-type semiconductor layer, first and second bonding pads electrically connected to the n-type and p-type semiconductor layers, respectively, and a first insulation layer at least partially disposed between the exposed portion of the n-type semiconductor layer exposed by the mesa and the second bonding pad, in which the exposed portion of the n-type semiconductor layer has a first portion having a shortest distance to the second bonding pad, the first insulation layer covers a portion of the p-type semiconductor layer disposed between the second bonding pad and the first portion of the n-type semiconductor layer, and the first insulation layer is disposed along an edge of the p-type semiconductor layer adjacent to the exposed portion of the n-type semiconductor layer.