Light Receiving Element Groove Isolation for Response Speed
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Solution Overview
Problem
Existing light receiving elements face challenges in increasing response speed due to increased carrier travel distance and the risk of short circuits between anode and cathode electrodes, particularly when the substrate thickness is increased or electrodes are adjacent.
Innovation Solution
A light receiving element design featuring a substrate with a light absorbing layer and a diffusion layer, surrounded by a window layer, where the anode and cathode electrodes are placed on the upper surface, and a groove or ion-implanted portion is used to prevent short circuits and reduce carrier travel distance, thereby enhancing response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the substrate is increased, then the mechanical strength is improved, but the distance through which carriers travel is increased and the response speed is reduced
Solution Approach 1:
The substrate structure is segmented into multiple functional layers: a first substrate layer, a light-absorbing layer, and a second substrate layer. The cathode electrode is positioned on the first substrate layer while the anode electrode is on the second substrate layer, creating separate carrier collection paths that reduce travel distance and improve response speed while maintaining overall structural strength through the layered configuration.
Solution Approach 2:
The invention transitions from a planar electrode arrangement to a three-dimensional layered structure. By stacking the light-absorbing layer between two substrate layers with electrodes on opposite sides, carriers have shorter vertical travel distances within each layer while the overall device thickness is maintained for mechanical strength.
2Device complexity
If the anode electrode and the cathode electrode are placed adjacent to each other, then the device complexity is reduced, but there is a possibility of a short circuit between the anode electrode and the cathode electrode
Solution Approach 1:
The device is segmented into distinct layers with the light-absorbing layer positioned between the anode and cathode electrodes. This spatial segmentation through vertical layering prevents direct contact between electrodes while maintaining a compact structure, eliminating short circuit risks without significantly increasing device complexity.
Solution Approach 2:
The light-absorbing layer acts as an intermediary barrier between the anode and cathode electrodes. This intermediate layer physically separates the two electrodes, preventing direct electrical contact and potential short circuits, while still allowing optical interaction for the intended photodetection function.
3Strength
If the thickness of the substrate is increased, then the mechanical strength is improved, but the current component delayed in response is increased
Solution Approach 1:
The substrate is segmented into multiple thin layers rather than one thick layer. Carriers generated in the light-absorbing layer have shorter distances to travel to reach their respective electrodes, reducing the delayed current component. The overall mechanical strength is maintained through the composite layered structure.
Solution Approach 2:
The invention uses a vertical stacking arrangement where the light-absorbing layer is positioned between two electrode-containing substrate layers. This three-dimensional arrangement reduces the effective carrier travel distance in each direction while maintaining the overall device thickness for mechanical strength, thereby reducing response delay.
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 prevents current component delays and short circuits, allowing for faster response times and reliable operation even with thicker substrates by isolating electrodes and optimizing carrier flow.
Implementation Method 1
a light absorbing layer of the first conduction type formed on the substrate and having a bandgap smaller than that of the substrate
Implementation Method 2
a diffusion layer of a second conduction type formed on a portion of the light absorbing layer
Implementation Method 3
an ion-implanted portion surrounding a boundary between the diffusion layer and the window layer as viewed in plan, extending through the window layer and the light absorbing layer as viewed in section, and shutting off a flow of carriers
Data Source
AI summary
A light receiving element includes a substrate of a first conduction type, a light absorbing layer of the first conduction type formed on the substrate, a diffusion layer of a second conduction type formed on a portion of the light absorbing layer, a window layer of the first conduction type formed on the light absorbing layer so as to surround the diffusion layer and having a bandgap larger than that of the light absorbing layer, an anode electrode formed on the diffusion layer, and a cathode electrode provided on the substrate so as to contact the substrate without contacting each of the window layer and the light absorbing layer, wherein a groove is formed which surrounds a boundary between the diffusion layer and the window layer as viewed in plan and extends through the window layer and the light absorbing layer as viewed in section.