Transparent Electrode Reflective LED Structure
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Solution Overview
Problem
Existing light emitting devices with reflective electrodes face challenges in achieving excellent electrical and optical characteristics due to reduced ohmic contact areas, current leakage, and diffusion of metal atoms into semiconductor layers, which deteriorate their performance.
Innovation Solution
A light emitting device structure featuring a transparent electrode interposed between the metal layer and semiconductor layers, forming an omnidirectional reflector with a stack of conductive oxide, insulation layer, and light-reflective metal, preventing metal diffusion and enhancing light reflection and electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective metal layer is formed on the p-type semiconductor layer through photolithography, then light reflection is achieved, but the ohmic contact area is reduced and Ag atoms diffuse into the semiconductor layer
Solution Approach 1:
An n-type semiconductor layer is introduced as an intermediary between the Ag reflective electrode and the p-type semiconductor layer. This intermediary layer prevents Ag atom diffusion into the p-type layer while maintaining ohmic contact, thereby resolving the contradiction between achieving light reflection and preventing deterioration of electrical characteristics
Solution Approach 2:
The electrode structure uses a composite design combining Ag reflective layer, n-type semiconductor layer, and p-type semiconductor layer. This multi-material structure enables simultaneous achievement of light reflection function and prevention of metal atom diffusion, resolving the technical contradiction
2Reliability
If the Ag electrode is used as the reflective electrode, then ohmic contact is formed, but current leakage increases due to Ag diffusion through defects
Solution Approach 1:
The n-type semiconductor layer serves as a protective intermediary that blocks the diffusion path of Ag atoms through defects in the p-type layer, preventing current leakage while preserving the ohmic contact functionality of the Ag electrode
3Ease of manufacture
If photolithography is used for patterning the reflective electrode, then the electrode structure is formed, but the Ag coverage area is reduced due to process margin
Solution Approach 1:
The n-type semiconductor layer acts as an intermediary that allows the Ag electrode to be formed with reduced coverage area while compensating for photolithography process margins. The intermediary layer ensures effective ohmic contact is maintained even when Ag coverage is reduced, resolving the contradiction between ease of manufacture and contact area
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 effectively prevents current leakage and improves luminous efficacy by using an omnidirectional reflector structure, ensuring better electrical and optical performance compared to traditional reflective electrode designs.
Implementation Method 1
a transparent electrode disposed on the second conductive type semiconductor layer and forming ohmic contact with the second conductive type semiconductor layer
Implementation Method 2
a metal layer at least partially covering the first insulation layer and extending to an upper surface of the second conductive type semiconductor layer
Implementation Method 3
A portion in which the transparent electrode, the first insulation layer and the metal layer are stacked may be an omnidirectional reflector
Data Source
AI summary
A light emitting device and a method of fabricating the same. The light emitting device includes: a light emitting structure including a first conductive type semiconductor layer, a second conductive type semiconductor layer, an active layer, and a partially exposed region of an upper surface of the first conductive type semiconductor layer; a transparent electrode disposed on the second conductive type semiconductor layer; a first insulation layer including a first opening and a second opening; a metal layer at least partially covering the first insulation layer; a first electrode electrically connected to the first conductive type semiconductor layer; and a second electrode electrically connected to the transparent electrode.