Lateral Intrinsic-Region Photodiode for Low-Loss Waveguide Detection
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Solution Overview
Problem
Current germanium photodiodes face limitations in opto-electrical bandwidth and responsivity due to light absorption by metal electrodes and doped regions, which restricts their performance in optical communication applications.
Innovation Solution
A diode design featuring a light-sensitive intrinsic region sandwiched laterally between p-doped and n-doped regions, where the intrinsic region is kept undoped and made of a material different from the doped regions, with a maximal lateral width of 400 nm or less, allowing for reduced dopant contamination and improved electrical field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If germanium photodiodes are produced with direct coupling to waveguide, then opto-electrical bandwidth is improved, but light absorption by metal electrodes and doped regions increases causing loss of light signal
Solution Approach 1:
The patent transitions from a vertical stacking architecture to a lateral sandwich architecture where the intrinsic region is positioned between doped regions in the lateral direction rather than vertically. This dimensional reorganization allows the light-sensitive intrinsic region to be shielded from metal electrode absorption while maintaining direct waveguide coupling for high bandwidth performance.
Solution Approach 2:
The intrinsic region serves as an intermediary layer that mediates between the metal electrodes and the light signal. By placing the light-sensitive intrinsic region laterally between doped regions, it acts as a protective barrier that prevents direct light absorption by metal electrodes and highly doped Ge regions, thereby reducing optical losses while maintaining electrical functionality.
2Reliability
If intrinsic region lateral width is reduced to 400 nm or less, then dopant contamination is reduced and electrical field distribution is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a precise parameter range for the intrinsic region lateral width (400 nm or less) to optimize device performance. This parameter control ensures reduced dopant contamination and improved electrical field distribution, which are critical for achieving the desired opto-electrical bandwidth and responsivity performance.
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 enhances opto-electrical bandwidth and responsivity, enabling faster receivers with reduced dark-current and material costs, while maintaining reasonable performance across various parameters.
Implementation Method 1
germanium (Ge) as a detector material due to its significantly better absorbance compared to silicon (Si) in the wavelength range used for optical communication (λ=1.3-1.6 μm)
Implementation Method 2
This results in losses because of light absorption by the metal electrodes and due to light absorption by free charge carriers in the doped Ge regions
Data Source
AI summary
A diode comprises a p-doped region, an n-doped region, and a light-sensitive intrinsic region sandwiched laterally between the p-doped region and the n-doped region in a direction transverse to a direction of light propagation in the diode. The p-doped region is made of a first material doped with a first type of dopant and the n-doped region is made of a third material doped with a second type of dopant. The first material includes Si or SiGe. The third material includes Si or SiGe. The intrinsic region is made of a second material, that includes Ge, GeSn, or SiGe. The intrinsic region has a maximal lateral extension between two lateral ends of the intrinsic region of equal to or below 400 nm. The p-doped region and the n-doped region are in-situ doped such that the intrinsic region is not doped when the diode is produced.