Nitride Semiconductor LED With Recessed Electron Blocking Layer
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Solution Overview
Problem
Nitride semiconductor LEDs have a low color rendering index (CRI) for white light emission, which is not effectively improved by existing technologies without the use of additional phosphors.
Innovation Solution
A light emitting device (LED) is designed with a specific structure including a first conductive semiconductor layer, an active layer with recesses, an electron blocking layer (EBL) having recesses and carrier injecting paths, and a second conductive semiconductor layer, where the EBL has a doping concentration ratio between regions and recesses optimized to enhance hole injection efficiency, allowing for improved CRI without additional phosphors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional phosphors are used to improve color rendering index, then CRI is improved, but device complexity increases
Solution Approach 1:
The patent extracts the phosphor conversion function from the system by directly emitting blue and green light through the active layer, eliminating the need for additional phosphor materials while maintaining high CRI. The active layer generates both blue light (450-499 nm) and green light (500-550 nm) simultaneously, removing the phosphor conversion step entirely.
Solution Approach 2:
The active layer is designed to perform multiple functions: generating blue light, generating green light, and providing the primary light source for high CRI white light emission. This multi-functional design eliminates the need for separate phosphor components while achieving the same or better color rendering performance.
2Reliability
If recess size is increased to improve carrier injection, then hole injection efficiency is improved, but light emission properties deteriorate
Solution Approach 1:
The patent applies different properties to different regions: the recess regions have high doping concentration (1×10^19 to 1×10^21 cm^-3) to enhance carrier injection, while the first regions between recesses have lower doping concentration (1×10^18 to 1×10^20 cm^-3) to maintain light emission properties. This local differentiation allows simultaneous optimization of both injection efficiency and light emission.
Solution Approach 2:
The patent transitions from a uniform planar structure to a three-dimensional structure with recesses and first regions, creating multiple carrier injection paths including vertical paths through recesses and lateral paths through first regions. This dimensional change enables improved carrier injection without compromising light emission from the active layer.
3Reliability
If doping concentration in recesses is increased to enhance carrier injection, then hole injection efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The electron blocking layer is segmented into distinct recess regions and first regions, each with independently controlled doping concentrations. The recess regions are doped at 1×10^19 to 1×10^21 cm^-3 while first regions are doped at 1×10^18 to 1×10^20 cm^-3. This segmentation allows precise control of doping in each region to optimize carrier injection without requiring ultra-precise uniform doping across the entire layer.
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 LED achieves an enhanced color rendering index (CRI) of R12, improved hole injection efficiency, and reduced droop phenomenon, leading to more efficient light emission and higher light properties even with increased recess size.
Implementation Method 1
Light emitting devices (LEDs) are compound semiconductor elements configured to convert electrical energy into light energy
Implementation Method 2
a ratio of a doping concentration of the first region to a doping concentration of the second recess is in a range of 1:0.8 to 1:1
Data Source
AI summary
A light-emitting device has a first conductive semiconductor layer; an active layer arranged on the first conductive semiconductor layer, and including a plurality of first recesses; an EBL arranged on the active layer, and including a plurality of second recesses arranged on the first recesses; and a second conductive semiconductor layer arranged on the EBL. The ratio of a first area doping concentration and a second recess doping concentration is from 1:0.8 to 1:1. The active layer emits first light and second light, the first light has a peak in a wavelength of 450 nm to 499 nm, and the second light has a peak in a wavelength of 500 nm to 550 nm.