AlGaInP LED Epitaxial Structure for Lower Absorption Red Emission
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Solution Overview
Problem
Red light-emitting LEDs with AlGaInP four-element material suffer from reduced luminous efficiency due to excessive light absorption caused by overly long intrinsic wavelengths, which is not adequately addressed by existing technologies.
Innovation Solution
The epitaxial structure of the light-emitting device incorporates a first type ohmic contact layer with Alx1Gay1InP and a first type window layer with Alx2Gay2InP, where the Al content of the ohmic contact layer is lower than that of the window layer, reducing the potential barrier height and intrinsic wavelength, thereby minimizing light absorption and enhancing luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the Al content in the n-type semiconductor layer is reduced to lower the potential barrier height and forward voltage, then the forward voltage is reduced, but the intrinsic wavelength becomes longer which exacerbates light absorption problem
Solution Approach 1:
The n-type semiconductor layer is segmented into multiple layers with different Al contents: a first n-type semiconductor layer with lower Al content (0.4-0.6) to reduce potential barrier height, and a second n-type semiconductor layer with higher Al content (0.6-0.8) adjacent to the active layer to reduce intrinsic wavelength and light absorption. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
Different regions of the n-type semiconductor layer are assigned different Al content compositions tailored to local requirements: the lower Al content region near the contact layer optimizes for electrical properties (lower potential barrier), while the higher Al content region near the active layer optimizes for optical properties (shorter intrinsic wavelength, reduced light absorption).
2Reliability
If a highly-doped GaAs layer is employed as an ohmic contact layer, then the ohmic contact is improved, but the intrinsic wavelength becomes overly long which reduces luminance due to excessive light absorption
Solution Approach 1:
The material composition parameter (Al content) is changed from the conventional GaAs (0 Al content) to AlGalnP with optimized Al content (0.4-0.6) in the first n-type semiconductor layer. This parameter change simultaneously achieves good ohmic contact properties while reducing the intrinsic wavelength to minimize light absorption and improve luminance.
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 reduces light absorption, enhances external quantum efficiency, and improves luminous intensity by adjusting the Al content and doping concentrations, resulting in a more efficient light-emitting device with lower forward voltage requirements.
Implementation Method 1
reduces light absorption, enhances external quantum efficiency, and improves luminous intensity by adjusting the Al content and doping concentrations
Data Source
AI summary
A light-emitting device includes: an epitaxial structure having a first surface and a second surface opposite to the first surface, and including a first type semiconductor layered unit that includes a first type window layer and a first type ohmic contact layer disposed at one side of the first type window layer; an active layer; and a second type semiconductor layered unit. The first type window layer is disposed between the first type ohmic contact layer and the active layer. The first type ohmic contact layer contains a material represented by Alx1Gay1InP, where 0≤x1≤1, 0≤y1≤1. The first type window layer contains a material represented by Alx2Gay2InP, where 0<x2≤1, 0≤y2≤1. The first type ohmic contact layer has an Al content lower than an Al content of the first type window layer. A light-emitting apparatus that includes a light-emitting device according to the disclosure is also disclosed.