Nitride Semiconductor Active Layer Structure for Efficiency Droop
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Solution Overview
Problem
Nitride semiconductor devices face efficiency droop and reduced effective light-emitting area during high power operation due to limited electron-hole recombination in the active layer, particularly in high current applications.
Innovation Solution
The active layer is optimized with an alternately-layered structure of quantum well and barrier layers, including unit multi-layer structures with a thick quantum barrier well and a super-lattice structure, which enhances carrier migration and reduces non-radiative recombination by adjusting layer thicknesses and quantum levels, thereby improving luminescence efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of quantum well layers is increased to improve light emission, then the effective light-emitting area increases, but the hole distribution becomes more remote from the p-type nitride semiconductor layer causing efficiency droop
Solution Approach 1:
The patent changes the thickness parameter of quantum barrier layers to 150 Å (thicker than conventional designs) to facilitate hole transport across multiple quantum well layers. This parameter modification enables effective carrier recombination even when multiple quantum well layers are stacked, thereby increasing the effective light-emitting area without suffering from efficiency droop.
Solution Approach 2:
The patent employs a composite structure consisting of multiple quantum well layers (first and second quantum well layers with different thicknesses) alternating with thick quantum barrier layers. This composite architecture allows electrons and holes to be effectively distributed and recombined across the entire active layer, solving the problem of limited effective light-emitting area while maintaining high recombination efficiency.
2Device complexity
If conventional quantum well structures are used, then the device structure is simple, but the effective light-emitting area is limited due to restricted electron-hole recombination
Solution Approach 1:
The patent segments the active layer into multiple quantum well layers (first quantum well layer adjacent to n-type layer, second quantum well layer adjacent to p-type layer) separated by thick quantum barrier layers. This segmentation allows independent optimization of electron and hole distribution in different regions, thereby expanding the effective light-emitting area across the entire active layer structure.
Solution Approach 2:
The patent extends the active layer structure in the vertical dimension by stacking multiple quantum well layers with different thicknesses and compositions. This dimensional expansion allows carriers to be injected and recombined throughout the entire thickness of the active layer, significantly increasing the effective light-emitting area compared to conventional single-layer structures.
3Illumination intensity
If high current operation is implemented to increase light output, then the brightness increases, but efficiency droop occurs due to reduced carrier recombination probability
Solution Approach 1:
The patent modifies the thickness parameters of quantum well layers and barrier layers to optimize carrier distribution under high current conditions. The first quantum well layer has a thickness of 20-60 Å while the second quantum well layer has a thickness of 10-50 Å, allowing efficient carrier recombination across the entire active layer even at high current densities, thereby preventing efficiency droop while maintaining high brightness.
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 significantly enhances luminescence efficiency during high power operation by increasing the effective light-emitting area and reducing efficiency droop, as demonstrated by improved energy conversion efficiencies with increased current supply.
Implementation Method 1
a tunneling quantum barrier layer disposed between the first and second quantum well layers
Implementation Method 2
nitride semiconductor devices, such as green or blue Light-Emitting Diodes (LEDs) and Laser Diodes (LDs), are widely used as a light source... based on electron-hole recombination
Data Source
AI summary
A nitride semiconductor device include an n-type nitride semiconductor layer; a p-type nitride semiconductor layer; and an active layer formed between the n-type and p-type nitride semiconductor layers. The active layer has an alternately-layered structure of a plurality of quantum well layers and a plurality of quantum barrier layers, each alternately stacked on each of the quantum well layers. The alternately-layered structure includes a unit multi-layer structure and a thick quantum barrier well. The unit multi-layer structure includes a first quantum well layer, a second quantum well layer formed, a tunneling quantum barrier layer and a crystal quality-improving layer. The thick quantum barrier well may be formed adjacent to the first and second quantum well layers, with a thickness thereof greater than that of the first and second quantum well layers.