Continuous compositional grading for realization of low charge carrier barriers in electro-optical heterostructure semiconductor devices
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Solution Overview
Problem
Existing semiconductor chips face challenges in achieving continuous electron mobility due to charge carrier barriers at interfaces between layers with different bandgap values, leading to reduced electron collection and speed.
Innovation Solution
The implementation of continuous compositional grading in the layered structure of semiconductor devices, where a grading layer with a continuous compositional transition is formed between semiconductor layers with different bandgap values, thereby reducing potential barriers and enhancing carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If semiconductor layers with different bandgap values are stacked to achieve specific optical and electrical functions, then device functionality is improved, but charge carrier barriers form at interfaces leading to reduced electron mobility and collection efficiency
Solution Approach 1:
The patent applies compositional grading within the grading layer to create local variations in material properties. By gradually changing the composition from InAlAs to InGaAs across the layer thickness, the bandgap transitions smoothly rather than abruptly, eliminating charge carrier barriers at interfaces while maintaining the functional benefits of different bandgap regions.
Solution Approach 2:
The grading layer acts as an intermediary between semiconductor layers with different bandgap values. This intermediate layer with continuously varying composition mediates the transition between dissimilar materials, preventing direct contact between mismatched bandgaps and thereby eliminating charge carrier barriers that would otherwise form at sharp interfaces.
2Speed
If a grading layer with continuous compositional grading is formed between semiconductor layers, then charge carrier barriers are reduced and electron mobility is improved, but device structure and manufacturing complexity increase
Solution Approach 1:
The patent segments the transition region into a dedicated grading layer with multiple sub-layers of gradually changing composition. This segmentation allows the complex compositional transition to be controlled in discrete steps during growth, making the manufacturing process more manageable while still achieving the desired continuous bandgap transition effect.
Solution Approach 2:
The patent systematically changes material composition parameters (indium, aluminum, gallium content) across the grading layer to achieve continuous compositional grading. By controlling these compositional parameters during epitaxial growth, the patent creates a smooth bandgap transition that reduces charge carrier barriers without requiring overly complex device structures.
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 effectively minimizes carrier trapping and recombination, leading to improved electron mobility and collection efficiency, thereby enhancing the performance of semiconductor devices such as photodetectors and electro-absorption modulators.
Implementation Method 1
a grading layer is formed onto the first semiconductor layer, wherein the grading layer comprises a plurality of layers defining a continuous compositional grading
Data Source
AI summary
Processes and devices for continuous compositional grading in photodetectors and electro-absorption modulators (EAM) are provided. An example photodetector includes a multi-layered structure comprising a collector region, an absorber region, a grading layer, and a peripheral layer, all aligned along a detection axis. The grading layer, positioned adjacent to the absorber region, includes multiple sub-layers that define a continuous compositional grading to facilitate smooth carrier transport and reduce recombination. Similarly, an example electro-absorption modulator (EAM) device includes a waveguide mesa formed on a semiconductor substrate, comprising a multi-quantum well (MQW) core layer, upper and lower near-core cladding layers, and upper and lower central cladding layers. The EAM device features both upper and lower grading layers, each positioned between the near-core cladding layers and the adjacent central cladding layers. These grading layers include multiple sub-layers that define a continuous compositional grading, facilitating smooth transitions between the MQW core and surrounding cladding layers.