UV LED Transparent Electrode and Dielectric Layer Design
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Solution Overview
Problem
Ultraviolet light-emitting diodes (UV LEDs) face challenges in achieving high light extraction efficiency due to difficulties in forming ohmic-contact with p-type AlGaN layers and absorption of ultraviolet light, leading to low external quantum efficiency and commercialization hurdles for short-wavelength nitride semiconductor LEDs.
Innovation Solution
The ultraviolet light emitting device incorporates a semiconductor laminate with a first and second conductivity-type AlGaN layers, active layers, and second conductivity-type nitride patterns with a smaller energy band gap, along with a transparent electrode layer and an omnidirectional reflector structure to enhance light extraction efficiency and ohmic-contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrode structure is used on p-type AlGaN layers, then device fabrication is simplified, but contact resistance is high and ohmic-contact formation is difficult
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: a transparent electrode layer (ITO) for ohmic contact, a reflective layer for light extraction, and a light-transmissive dielectric layer for optical management. This segmentation allows each layer to optimize its specific function, achieving low contact resistance while maintaining fabrication feasibility through standardized layer-by-layer deposition processes
Solution Approach 2:
The patent employs composite material structures, specifically combining ITO (transparent conducting oxide) with metal reflective layers and dielectric materials. This composite approach enables simultaneous achievement of electrical conductivity, optical reflectivity, and light extraction enhancement, resolving the contradiction between contact quality and fabrication complexity
2Loss of energy
If standard light extraction structures are used, then device structure is simple, but light extraction efficiency is low due to UV absorption
Solution Approach 1:
A light-transmissive dielectric layer is introduced as an intermediary between the semiconductor layers and the external environment. This dielectric layer has optimized refractive index to reduce total internal reflection and enhance light extraction efficiency in the UV range, while being transparent to UV wavelengths to avoid absorption losses. The intermediary layer resolves the contradiction by providing optical management without requiring complex structural modifications
Solution Approach 2:
The patent optimizes optical parameters including refractive index matching, layer thickness, and material composition to enhance UV light extraction. By changing these parameters rather than structural complexity, the patent achieves improved light extraction efficiency while maintaining relatively simple device architecture
3Object-affected harmful factors
If p-type AlGaN layers with high Al composition are used, then UV light absorption is reduced, but ohmic-contact formation becomes more difficult
Solution Approach 1:
The patent extracts the contact formation function from the p-type AlGaN layer itself by introducing a separate transparent electrode layer (ITO). This allows the p-type AlGaN layer to maintain high Al composition for UV transparency without compromising contact quality, as the ITO layer provides the necessary ohmic contact interface. The contact formation function is separated from the optical function, resolving the contradiction
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
This configuration improves light extraction efficiency and reduces contact resistance, enabling the production of UV LEDs with enhanced performance and commercial viability by using ITO as a transparent electrode and a light-transmissive dielectric layer in conjunction with a metal electrode.
Implementation Method 1
enhance light extraction efficiency
Implementation Method 2
reduces contact resistance
Data Source
AI summary
An ultraviolet light emitting device including a first conductivity-type AlGaN semiconductor layer; an active layer disposed on the first conductivity-type AlGaN semiconductor layer and having an AlGaN semiconductor; a second conductivity-type AlGaN semiconductor layer disposed on the active layer and having an upper surface divided into a first region and a second region; second conductivity-type nitride patterns disposed on the first region of the second conductivity-type AlGaN semiconductor layer and having an energy band gap that is smaller than an energy band gap of the second conductivity-type AlGaN semiconductor layer; a transparent electrode layer covering the second conductivity-type nitride patterns and the second region of the second conductivity-type AlGaN semiconductor layer; a light-transmissive dielectric layer disposed on the transparent electrode layer between the second conductivity-type nitride patterns; and a metal electrode disposed on the transparent electrode layer overlying the second conductivity type nitride patterns and on the light-transmissive dielectric layer.