GaN LED Border Layer Band Gap Gradient for Efficiency Droop
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Solution Overview
Problem
Semiconductor light emitting devices face issues with film quality deterioration in the active layer, leading to degraded light characteristics and efficiency droop phenomena, particularly in group III nitride semiconductor devices.
Innovation Solution
A semiconductor light emitting device structure is implemented with a specific configuration including an n-type GaN contact layer, an n-type super-lattice layer, a border layer with decreasing band gap energy, an active layer with a multiple quantum well structure, and a p-type AlxInyGazN layer, along with a p-type GaN layer, and the inclusion of dopants like silicon and magnesium to enhance light emission efficiency and prevent agglomeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional active layer structure is used, then device simplicity is maintained, but film quality deterioration and agglomeration occur leading to degraded light characteristics
Solution Approach 1:
The active layer is divided into multiple quantum well layers (five or more) and quantum barrier layers (four or more) with different compositions and thicknesses. This segmentation allows each sub-layer to have optimized properties, preventing agglomeration and maintaining film quality while improving light emission characteristics
Solution Approach 2:
Different regions of the active layer have different compositions and thicknesses to achieve local optimization. The quantum well layers have specific thicknesses (5-20 nm) and compositions tailored for electron-hole recombination, while barrier layers have different properties for carrier confinement, preventing uniform agglomeration throughout the layer
2Power
If dopant concentration is increased to improve light emission, then efficiency increases, but efficiency droop phenomenon occurs at high currents
Solution Approach 1:
The dopant concentration is varied dynamically across different layers and positions. The n-type GaN layer has dopant concentration of 2×10^18 to 9×10^19 cm^-3, while the p-type GaN layer has 1×10^18 to 9×10^21 cm^-3, with the concentration increasing or decreasing in the thickness direction. This dynamic doping strategy optimizes carrier injection while preventing efficiency droop
Solution Approach 2:
The dopant concentration parameter is changed across different layers and positions to optimize performance. Silicon doping in n-type layers and magnesium doping in p-type layers are controlled with specific concentration ranges and thickness-dependent variations, allowing efficient light emission without efficiency droop
3Reliability
If band gap energy is uniform throughout the structure, then manufacturing is simplified, but light characteristics are degraded due to particle agglomeration
Solution Approach 1:
The border layer has band gap energy that decreases in a direction away from the first conductivity-type semiconductor layer, creating a gradient structure. This local variation in band gap energy prevents particle agglomeration by creating energy barriers, while the graded structure allows for controlled manufacturing processes
Solution Approach 2:
The band gap energy parameter is changed systematically across the border layer and active layer structure. The decreasing band gap energy in the border layer and the alternating band gap structures in quantum wells and barriers create favorable conditions for preventing agglomeration while maintaining manufacturability
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 proposed structure improves light characteristics, reduces efficiency droop, and maintains high light emission efficiency by preventing film quality deterioration and agglomeration, specifically by controlling the band gap energy and dopant concentration.
Implementation Method 1
an n-type GaN layer disposed on the n-type GaN contact layer, doped with silicon (Si) acting as an n-type dopant... and a p-type GaN layer disposed on the p-type AlxInyGazN layer, doped with magnesium (Mg) acting as a p-type dopant
Implementation Method 2
Light emitting diodes (LEDs) are semiconductor light emitting devices capable of generating various colors of light through the recombination of electrons and holes at junctions between first and second conductivity-type semiconductor layers when a current is applied thereto
Implementation Method 3
a border layer disposed on the first conductivity-type semiconductor layer and having band gap energy decreasing in a direction away from the first conductivity-type semiconductor layer
Data Source
AI summary
A semiconductor light emitting device includes an n-type semiconductor layer, a border layer disposed on the n-type semiconductor layer, having band gap energy decreasing in a single direction, and represented by an empirical formula AlxInyGa1−x−yN (0≦x≦0.1, 0.01≦y≦0.1), an active layer disposed on the border layer and having a structure in which one or more InGaN layers and one or more GaN layers are alternately stacked, and a p-type semiconductor layer.