Waveguide Photodiode Layout for High Bandwidth and Responsivity
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Solution Overview
Problem
Photodiodes face challenges in achieving high responsivity and bandwidth due to competition between semiconductor material absorption and metal electrode absorption, leading to degraded quantum efficiency, especially in high bandwidth applications where metal electrodes must be close to the optical signal.
Innovation Solution
Incorporating an elongate doped and conductive semiconductor structure that extends beyond the semiconductor material's sides, allowing metal contacts to be offset from the absorbing region, reducing absorption competition and enabling thinner semiconductor regions for adequate carrier transit without sacrificing responsivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If metal electrodes are placed close to the optical signal to achieve high bandwidth, then carrier transit bandwidth is improved, but metal electrode absorption increases and degrades quantum efficiency
Solution Approach 1:
An intrinsic semiconductor layer is introduced as an intermediary between the metal electrode and the absorbing semiconductor material. This intrinsic layer allows the metal electrode to be positioned close to the optical signal for high bandwidth while preventing direct metal absorption of photons, thus maintaining high quantum efficiency. The intrinsic layer acts as a mediator that enables both high-speed carrier collection and efficient optical absorption.
2Speed
If semiconductor material thickness is reduced to increase bandwidth, then carrier transit time is decreased, but optical absorption is insufficient and responsivity degrades
Solution Approach 1:
The patent extends the semiconductor structure laterally beyond the vertical absorption region, creating wing-like structures that protrude from the sides of the absorbing semiconductor material. This lateral extension provides additional pathways for carrier collection without requiring increased vertical thickness, thus maintaining high bandwidth while ensuring adequate optical absorption and responsivity.
3Speed
If semiconductor structure is extended laterally to improve carrier collection, then bandwidth is improved, but device complexity increases
Solution Approach 1:
The semiconductor structure is segmented into distinct functional regions: a vertical absorption region for optical signal capture and lateral wing structures for carrier collection. This segmentation allows each region to be optimized independently - the vertical region for absorption efficiency and the lateral extensions for rapid carrier extraction - thereby achieving high bandwidth without excessive overall complexity.
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 increases carrier transit bandwidth while maintaining high responsivity by minimizing the impact of metal contacts on optical absorption, improving photodiode performance across various wavelengths.
Implementation Method 1
a semiconductor layer comprising an semiconductor material, the semiconductor layer disposed on the substrate and in communication, such as optical or electrical communication, with at least a region of the substrate
Implementation Method 2
the elongate portion is doped with N+ dopants
Data Source
Figure 1A~1C
Figure 2~4
Figure 5A~5F
AI summary
In part, in one aspect, the disclosure relates to a photodiode (100). The photodiode (100) may include a substrate (104); a semiconductor layer (102) comprising a semiconductor material, the semiconductor layer disposed on the substrate (104) and in communication with at least a region of the substrate, the semiconductor layer having a first side , a second side, and an upper surface, the semiconductor layer having a height; a semiconductor structure (110) partially disposed on the upper surface, the semiconductor structure (110) comprising at least one elongate portion that extends beyond the first side and along a portion of the upper surface of the semiconductor layer; and a metal contact (106a) that is in electrical connection with the elongate portion of the semiconductor structure (110).