LED-Photodiode Epitaxy Layout for Stokes Shift Alignment
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Solution Overview
Problem
Current optoelectronic devices comprising LEDs and photodiodes face inefficiencies due to the Stokes shift, where the optimal emission wavelength of LEDs is shifted away from the optimal absorption wavelength of photodiodes, affecting sensitivity and efficiency.
Innovation Solution
The method involves forming an active semiconductor stack common to both LEDs and photodiodes through epitaxy, followed by the creation of trenches that differentiate their lateral dimensions, and adjusting the carrier density to align the emission and absorption peaks, thereby compensating for the Stokes shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a common epitaxy step is used to form both LED and photodiode stacks, then manufacturing complexity is reduced and productivity is improved, but the Stokes shift causes misalignment between emission and absorption peaks, worsening system efficiency
Solution Approach 1:
The patent applies local quality by creating different lateral dimensions for LED and photodiode regions within the same epitaxial stack. The LED region has a first lateral dimension while the photodiode region has a second lateral dimension that is larger than the first. This local differentiation allows each region to be optimized for its specific function (emission vs. absorption) while maintaining wavelength alignment, resolving the contradiction between manufacturing efficiency and system efficiency.
2Device complexity
If the lateral dimensions of LED and photodiode are made equal, then device complexity is reduced, but the Stokes shift causes wavelength misalignment, worsening measurement precision
Solution Approach 1:
The patent applies asymmetry by intentionally making the lateral dimensions of the LED region and photodiode region different. The photodiode region has a larger lateral dimension than the LED region, creating an asymmetric structure that compensates for the Stokes shift. This asymmetric design ensures that the emission peak of the LED aligns with the absorption peak of the photodiode, improving wavelength alignment precision while maintaining relatively simple device structure.
3Measurement precision
If carrier density is increased to align emission and absorption peaks, then wavelength alignment is improved, but internal electric field stress increases, worsening device reliability
Solution Approach 1:
The patent applies parameter changes by modifying the lateral dimension parameter of the photodiode region to be larger than that of the LED region. This geometric parameter change alters the optical field distribution and carrier density distribution within the active layers, enabling peak alignment without requiring excessive carrier injection. The parameter change approach provides a more reliable solution compared to simply increasing carrier density, as it avoids excessive electric field stress while achieving the desired wavelength alignment.
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 approach enhances the alignment of emission and absorption peaks, improving the efficiency of the LED-photodiode system by reducing internal electric field stress in the LED stack and increasing carrier density, thus enhancing signal-to-noise ratio and overall system performance.
Implementation Method 1
forming, by epitaxy, an active emission and reception semiconductor stack common to the LED and to the photodiode
Implementation Method 2
devices comprising one or a plurality of LEDs configured to emit light signals
Implementation Method 3
one or a plurality of photodiodes configured to receive and measure signals emitted by the LEDs
Data Source
AI summary
A method of manufacturing an optoelectronic device including at least one LED and at least one photodiode, including the following steps: a) forming a semiconductor support stack including at least one doped semiconductor layer; b) simultaneously forming, during a common epitaxy step, an active emission semiconductor stack of the LED and an active reception semiconductor stack of the photodiode; c) forming trenches delimiting first and second support pads; and d) porosifying the doped semiconductor layer in the first support pad without porosifying this layer in the second support pad, or porosifying the doped semiconductor layer in the second support pad without porosifying this layer in the first support pad.