Semiconductor Photodiode Evanescent Coupling Diffusion Barrier
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Solution Overview
Problem
Semiconductor photodiodes with p-i-n diode structures face issues due to dopant diffusion from the p-contact layer into adjacent layers, leading to deterioration of electrical properties and increased noise, which affects their sensitivity and RF bandwidth.
Innovation Solution
A semiconductor photodiode design with a doped optical waveguide that acts as a diffusion barrier, preventing dopant diffusion from the contact layer into the waveguide, while maintaining efficient evanescent light coupling and minimizing impact on optical properties, thereby enhancing intrinsic sensitivity and reducing the need for electrical amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the n-contact is arranged above the absorber layer and the p-contact is located below the absorber layer to avoid light coupling via the n-contact and multiplier layer, then the light coupling efficiency is improved, but dopant diffusion occurs from the p-contact layer into adjacent layers causing deterioration of electrical properties
Solution Approach 1:
The patent introduces an intrinsic or lightly-doped semiconductor layer as an intermediary between the p-contact layer and the optical waveguide. This intermediate layer physically separates the heavily doped p-contact from the waveguide region, blocking dopant diffusion while still allowing electrical contact and light propagation. The intermediate layer acts as a diffusion barrier that prevents contaminant migration without compromising the light coupling efficiency achieved by the inverted contact structure.
Solution Approach 2:
The patent divides the semiconductor structure into distinct functional zones with different doping levels. The p-contact layer remains heavily doped for electrical contact, while the intermediate layer is intrinsic or lightly-doped to serve as a diffusion barrier. This segmentation allows each layer to optimize its specific function: the p-contact provides electrical access, the intermediate layer prevents dopant migration, and the waveguide maintains optical properties.
2Reliability
If doping is applied to the optical waveguide to create a diffusion barrier, then dopant diffusion is prevented, but the optical properties of the waveguide may be affected
Solution Approach 1:
The patent applies doping selectively to specific regions of the semiconductor structure rather than uniformly throughout. The p-contact layer maintains heavy doping for electrical contact, while the intermediate layer is kept intrinsic or lightly-doped to preserve optical transparency. The waveguide region receives minimal or localized doping only where necessary for diffusion prevention, maintaining low doping concentrations in regions critical for light propagation to minimize impact on optical properties.
Solution Approach 2:
The patent changes the doping concentration parameter across different layers and regions. By transitioning from heavy doping in the p-contact layer to intrinsic or light doping in the intermediate layer and waveguide regions, the patent optimizes both electrical and optical performance. The doping concentration is carefully controlled to provide sufficient diffusion barrier functionality while keeping absorption and scattering losses minimal in the optical path.
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
The solution achieves higher intrinsic sensitivity and reduced noise, leading to increased RF bandwidth with minimal impact on optical properties, allowing for efficient operation comparable to p-i-n photodiodes.
Implementation Method 1
an optical waveguide via which light can evanescently be coupled into the light-absorbing layer
Implementation Method 2
the optical waveguide at least sectionally has a doping which produces a diffusion barrier counteracting a diffusion of dopant of the contact layer into the optical waveguide
Data Source
AI summary
A semiconductor photodiode, including a light-absorbing layer; an optical waveguide via which light can evanescently be coupled into the light-absorbing layer, and a doped contact layer arranged between the light-absorbing layer and the optical waveguide. The optical waveguide at least sectionally has a doping which produces a diffusion barrier counteracting a diffusion of dopant of the contact layer into the optical waveguide.