LED Epitaxial Structure Doping Gradient Stress Management
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Solution Overview
Problem
Conventional light emitting diode (LED) manufacturing methods face challenges in achieving optimal epitaxial structure thickness and doping concentration distribution, leading to stress accumulation and defects in the light emitting layer, which affect emission uniformity, intensity, and reliability.
Innovation Solution
A light emitting device with an epitaxial structure featuring a first semiconductor sublayer with a heavily doped part and a lightly doped part, where the doping concentration of the first type dopant in the heavily doped part is between 10^17 and 10^18 atoms/cm^3, and in the lightly doped part is less than 10^17 atoms/cm^3, reducing stress and defects by buffering and releasing accumulated stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional epitaxial method is used to form N-type semiconductor layer, light emitting layer, and P-type semiconductor layer, then the basic LED structure is obtained, but stress accumulation and defects occur in the light emitting layer affecting emission uniformity and reliability
Solution Approach 1:
The N-type semiconductor layer is segmented into multiple sublayers with different doping concentrations. Specifically, it includes a first N-type sublayer with first doping concentration, a second N-type sublayer with second doping concentration lower than the first, and a third N-type sublayer with third doping concentration higher than the second. This segmentation allows stress to be distributed and managed across different layers, preventing stress accumulation and defects in the light emitting layer.
Solution Approach 2:
Different regions of the N-type semiconductor layer are assigned different doping concentrations tailored to specific functional requirements. The first N-type sublayer near the light emitting layer uses lower doping concentration to reduce stress, while the third N-type sublayer uses higher doping concentration for better electrical contact. This local quality optimization resolves the contradiction between stress management and electrical performance.
2Reliability
If doping concentration is increased to improve electrical performance, then electrical conductivity improves, but stress accumulation increases leading to defects
Solution Approach 1:
The doping concentration parameter is changed across different sublayers of the N-type semiconductor layer. The first N-type sublayer has a lower doping concentration (first doping concentration) to minimize stress, while the third N-type sublayer has a higher doping concentration (third doping concentration) to enhance electrical conductivity. This parameter variation across layers allows the system to achieve both low stress and good electrical performance.
3Illumination intensity
If epitaxial structure thickness is optimized for performance, then emission intensity improves, but manufacturing precision becomes difficult to control
Solution Approach 1:
Instead of controlling the thickness of a single thick N-type layer, the structure is segmented into multiple thinner sublayers (first, second, and third N-type sublayers) with different doping concentrations. This segmentation makes the epitaxial growth process more controllable and precise, as each sublayer can be grown with better thickness control, while collectively achieving the desired emission intensity.
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 solution improves emission uniformity, intensity, and breakdown voltage, while reducing current leakage and enhancing the overall electrical performance and reliability of the light emitting device by effectively managing stress through the doping concentration gradient.
Implementation Method 1
reducing stress and defects by buffering and releasing accumulated stress
Data Source
AI summary
A light emitting device includes an epitaxial structure. The epitaxial structure includes a first type semiconductor layer, a second type semiconductor layer and a light emitting layer. The first type semiconductor layer includes a first semiconductor sublayer. The light emitting layer is disposed between the first type semiconductor layer and the second type semiconductor layer. The first semiconductor sublayer includes a heavily doped part and a lightly doped part which are doped by a first type dopant. A doping concentration of the first type dopant in the heavily doped part is equal to 1018 atoms/cm3 or between 1017 atoms/cm3 and 1018 atoms/cm3. A doping concentration of the first type dopant in the lightly doped part is less than or equal to 1017 atoms/cm3.