Waveguide Photodiode Layout With Offset Contacts for High 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 are close to the optical signal.
Innovation Solution
The introduction of an elongate doped semiconductor structure that extends beyond the semiconductor material's sides, allowing metal contacts to be offset and reducing absorption competition, thereby maintaining high responsivity with thinner semiconductor regions.
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 speed is improved, but quantum efficiency and responsivity are degraded due to absorption competition
Solution Approach 1:
The patent introduces an elongate semiconductor structure that extends in a lateral dimension beyond the semiconductor material's sides, creating a three-dimensional configuration. This allows metal contacts to be offset laterally while maintaining electrical connection, thereby separating the metal electrodes from the optical signal path in the lateral dimension while preserving vertical carrier transit efficiency.
Solution Approach 2:
The elongate doped semiconductor structure serves as an intermediary between the metal contacts and the intrinsic semiconductor material. It provides electrical connection to the metal electrodes while physically separating them from the optical signal region, thus mediating the conflict between electrical connection requirements and optical absorption efficiency.
2Speed
If semiconductor layer thickness is reduced to improve bandwidth, then carrier transit time is decreased, but optical absorption and responsivity are reduced
Solution Approach 1:
The patent compensates for reduced vertical absorption in thinner semiconductor layers by introducing lateral extension through elongate structures. This dimensional transition allows the photodiode to maintain effective absorption volume while reducing vertical thickness for faster carrier transit.
Solution Approach 2:
The patent employs a composite structure combining intrinsic semiconductor material for optical absorption with doped semiconductor regions for electrical conduction and structural support. This composite approach allows optimization of each region's thickness independently - thin intrinsic region for fast transit, thicker doped regions for electrical functionality.
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 enhances carrier transit without sacrificing responsivity, improving photodiode performance by reducing parasitic resistance and capacitance while maintaining high bandwidth.
Implementation Method 1
a portion of the semiconductor material is in optical communication with a region of the optical waveguide
Implementation Method 2
the at least one elongate portion is doped with N+ dopants
Data Source
AI summary
In part, in one aspect, the disclosure relates to a photodiode. The photodiode may include a substrate; a semiconductor layer comprising an semiconductor material, the semiconductor layer disposed on the substrate 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 partially disposed on the upper surface, the semiconductor structure 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 that is in electrical connection with the elongate portion of the semiconductor structure.