Oblique-Waveguide Photodetector for High Responsivity and Bandwidth
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Solution Overview
Problem
Photo detectors face a trade-off between high responsivity and low dark current, where increased absorption length enhances responsivity but also increases dark current, thereby reducing bandwidth.
Innovation Solution
A photo detector design featuring a germanium PIN photodetector with an obliquely connected waveguide and insulation layers, creating a Total Internal Reflection (TIR) effect that increases the path length of incident light within the exciting layer, thereby enhancing responsivity while shortening the detector length to reduce dark current and increase bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the absorption length is increased to enhance responsivity, then the responsivity is improved, but the dark current increases and bandwidth reduces
Solution Approach 1:
The patent introduces an oblique connection between the waveguide and the exciting layer, creating a three-dimensional light path configuration. This dimensional change allows light to traverse a longer effective path through the absorbing material without increasing the physical length of the detector, thereby enhancing responsivity while controlling dark current and maintaining bandwidth.
Solution Approach 2:
The oblique waveguide configuration creates a curved or angled light path through the exciting layer rather than a straight linear path. This curvature principle increases the interaction length between light and the photoactive material, improving absorption efficiency and responsivity without proportionally increasing the detector's physical dimensions and associated dark current.
2Measurement precision
If the absorption length is increased to enhance responsivity, then the responsivity is improved, but the bandwidth reduces
Solution Approach 1:
By transitioning from a linear to an oblique three-dimensional configuration, the patent decouples the relationship between physical length and optical path length. This allows the detector to achieve high responsivity through increased optical interaction without proportionally increasing the physical size that would increase capacitance and reduce bandwidth.
3Object-generated harmful factors
If the detector length is shortened to reduce dark current, then the dark current is reduced, but the responsivity decreases
Solution Approach 1:
The oblique waveguide configuration enables the detector to maintain a compact physical footprint (short detector length) while achieving an extended effective optical path length through the exciting layer. This dimensional strategy reduces dark current associated with longer physical structures while preserving responsivity through increased light-matter interaction.
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 design achieves higher responsivity and bandwidth while minimizing dark current, by optimizing the path length of incident light and reducing the detector length, thus balancing the trade-off between these parameters.
Implementation Method 1
creating a Total Internal Reflection (TIR) effect that increases the path length of incident light within the exciting layer
Implementation Method 2
A photo detector may receive a light and transform the light into a current
Data Source
AI summary
A photo detector includes a substrate, an exciting layer, a first insulation layer, a second insulation layer and a waveguide. The substrate has a recess. The exciting layer is formed in the recess and having a light incident surface and, a first side and a second side opposite to the first side. The first insulation layer is formed in the substrate and disposed on the first side of the exciting layer. The second insulation layer is formed in the substrate and disposed on the second side of the exciting layer. The waveguide is obliquely connected to the light incident surface of the exciting layer. There is an acute angle included between the light incident surface and an extension direction of the waveguide.