Vertical LED Transparent Electrode with Conducting Filaments
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Solution Overview
Problem
Current light emitting devices face issues with current concentration and reduced light extraction efficiency, particularly in UV wavelength ranges, due to the trade-off between conductivity and transmittance in existing transparent electrodes, which limits the performance of vertical-type LEDs.
Innovation Solution
A vertical-type light emitting device with a transparent electrode made from a resistance change material that forms conducting filaments upon applying a threshold voltage, combined with a current spreading layer using CNT or graphene, to ensure uniform current injection and enhanced light transmittance across the entire wavelength range, including UV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent electrode made from conventional transparent conductive oxide (TCO) materials is used, then light transmittance is maintained, but electrical conductivity is insufficient leading to current concentration
Solution Approach 1:
The patent uses a composite structure consisting of a transparent insulating material layer and a transparent conductive material layer. The TCO layer is formed on the n-type semiconductor layer, and a patterned transparent conductive material is deposited on the TCO layer. This composite structure combines the high transmittance of the transparent insulating material with the electrical conductivity of the TCO and patterned conductive material, resolving the contradiction between maintaining light transmittance and achieving sufficient electrical conductivity to prevent current concentration.
2Reliability
If the contact area of the n-type electrode is increased to improve current dispersion, then current uniformity is improved, but light extraction efficiency is deteriorated due to light blocking
Solution Approach 1:
The patent applies local quality by creating a patterned transparent conductive material layer with different transparency regions. The pattern includes transparent regions positioned over the n-type electrode contact areas to improve current dispersion, and highly transparent regions positioned over the light extraction areas to maintain light extraction efficiency. This spatially differentiated structure allows different parts of the electrode to have different properties - higher conductivity where needed for current dispersion and higher transmittance where needed for light extraction.
3Reliability
If a transparent conductive material layer is added to improve conductivity, then current concentration is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent introduces a transparent insulating material layer as an intermediary between the n-type semiconductor layer and the patterned transparent conductive material. This intermediary layer serves multiple functions: it provides a uniform base layer that facilitates controlled deposition of the patterned conductive material, electrically isolates the semiconductor layer to prevent unwanted current paths, and maintains optical transparency. This intermediary structure simplifies the manufacturing process by enabling standard deposition techniques while achieving the desired current distribution uniformity.
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 addresses current concentration and improves light extraction efficiency by allowing current to spread evenly and maintaining high conductivity without thermal treatment, enhancing both electrical and optical characteristics of the light emitting device.
Implementation Method 1
a transparent electrode formed on the first semiconductor layer by using a transparent insulating material of which a resistance state is to be changed from a high resistance state into a low resistance state according to an applied electric field
Implementation Method 2
maintaining high conductivity without thermal treatment, enhancing both electrical and optical characteristics of the light emitting device
Data Source
AI summary
Provided is a vertical type light emitting device and a method of manufacturing the same. A transparent electrode having high transmittance with respect to light in the entire range and constructed by using a resistance change material of which resistance state is to be changed from a high resistance state to a low resistance state if a voltage exceeding a threshold voltage inherent in a material is applied so that conducting filaments are formed is formed between an electrode pad and a semiconductor layer of a light emitting device. The transparent electrode has high transmittance with respect to the light in a UV wavelength range as well as in a visible wavelength range generated in the light emitting device. Since the conductivity of the transparent electrode is heightened due to the formation of the conducting filaments, the transparent electrode has good ohmic contact characteristic with respect to a semiconductor layer.