LED Epitaxial Structure With Large V-Pits for Better Hole Injection
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Solution Overview
Problem
Nitride-based light emitting diodes (LEDs) face poor hole injection efficiency in areas without v-pit formation, leading to higher forward operating voltage and efficiency droop under large currents, limiting the improvement of photoelectric characteristics.
Innovation Solution
A light emitting diode structure with an epitaxial semiconductor layer comprising an N-type nitride layer, a v-pit emergence layer, a strain adjustment layer, and a P-type nitride layer, where the v-pit emergence layer and strain adjustment layer include indium, and the v-pits are doped with carbon, enhancing hole injection efficiency by forming large v-pits that reduce the effective c-plane area and increase hole injection at side walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If v-pit formation technique is utilized in nitride based LEDs, then hole injection efficiency is improved in v-pit areas, but hole injection efficiency remains poor in areas without v-pit formation
Solution Approach 1:
The patent applies local quality by creating v-pits only in specific areas of the active layer where enhanced hole injection is needed, while maintaining the original structure in other areas. The v-pit emergence layer is selectively positioned to form v-pits at locations with poor hole injection, providing localized improvement without altering the entire device structure.
Solution Approach 2:
The v-pit emergence layer acts as an intermediary between the N-type nitride layer and the active layer. This intermediate layer facilitates hole injection by providing a preferential pathway for holes to reach the active region, thereby improving overall hole injection efficiency while maintaining structural integrity.
2Ease of manufacture
If conventional LED structure is used, then manufacturing is simpler, but forward operating voltage is higher and efficiency droop occurs under large currents
Solution Approach 1:
The active layer is segmented into multiple quantum wells with varying indium compositions, creating distinct regions with different bandgap energies. This segmentation allows for optimized carrier injection and recombination in each region, reducing the overall forward operating voltage and minimizing efficiency droop under high current conditions.
Solution Approach 2:
The patent changes the indium composition parameter across different layers of the active layer, creating a gradient structure that optimizes hole injection efficiency. By adjusting the indium content in the v-pit emergence layer and active layer, the patent achieves lower forward operating voltage while maintaining ease of manufacture through standard epitaxial growth techniques.
3Reliability
If indium content in strain adjustment layer is increased, then hole injection efficiency is improved, but strain management becomes more challenging
Solution Approach 1:
The strain adjustment layer is positioned locally between the v-pit emergence layer and the active layer, providing strain compensation only where needed. By concentrating the strain adjustment function in this specific location rather than throughout the entire structure, the patent achieves improved hole injection efficiency while maintaining strain stability in other critical regions.
Solution Approach 2:
The patent uses composite material structure combining the v-pit emergence layer, strain adjustment layer with specific indium content, and active layer. This composite approach allows the strain adjustment layer to compensate for lattice mismatch and strain effects, enabling higher indium content in the active layer for improved hole injection while maintaining overall structural stability.
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 hole injection efficiency, decreases operating voltage, and enhances light emission efficiency, reducing the droop effect under high current conditions, with external quantum efficiency increased by 3.5% to 5% and operating voltage reduced by 0.02V.
Implementation Method 1
forming large v-pits that reduce the effective c-plane area and increase hole injection at side walls
Implementation Method 2
the v-pit emergence layer is doped with carbon (C) at a doping concentration that is no less than 7×1016/cm3
Implementation Method 3
electron and hole recombination efficiency in an active layer of the light emitting diode which is known as the internal quantum efficiency
Data Source
AI summary
A light emitting diode includes an epitaxial semiconductor layer including an N-type nitride layer, a v-pit emergence layer, a strain adjustment layer, an active layer, and a P-type nitride layer that are sequentially stacked in that order. The active layer has a plurality of barrier layers and a plurality of well layers that are alternatively stacked. The epitaxial semiconductor layer includes a v-pit. The v-pit has an opening that is located at a topmost one of the barrier layers of the active layer, and has a width that is greater than 260 nm. The v-pit emergence layer is doped with carbon (C) at a doping concentration that is no less than 7×1016/cm3. A light emitting device includes the light emitting diode.