Infrared Detector Structure With Lateral SiGe Absorber Coupling
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Solution Overview
Problem
Conventional silicon-based photodiodes have low responsivity and limited spectral responsivity for wavelengths higher than 1100 nm due to their bandgap, resulting in reduced sensitivity for infrared detection.
Innovation Solution
A semiconductor device with a lateral absorber region made of strained Silicon-Germanium alloy and an optical coupling layer that deflects incident light, extending absorption into the near-infrared range and increasing the absorption volume, thereby enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional silicon-based photodiodes are used with vertical layer stack structure, then the device structure is simple and manufacturing is easy, but the spectral responsivity is limited for wavelengths higher than 1100 nm due to silicon bandgap
Solution Approach 1:
The patent transitions from a conventional vertical absorption geometry to a lateral absorption geometry. The optical coupling layer with optical couplers directs incident light laterally into the absorber region, changing the dimension of light absorption from vertical to lateral. This enables extended near-infrared detection beyond 1100 nm while maintaining compatibility with standard silicon manufacturing processes.
Solution Approach 2:
The patent employs a composite structure combining silicon-based absorber material with an optical coupling layer containing optical couplers. The optical coupling layer acts as an intermediary that modifies the optical path, enabling the silicon absorber to detect wavelengths beyond its native bandgap limitation. This composite approach extends spectral responsivity into the near-infrared range while maintaining ease of manufacture.
2Manufacturing precision
If the absorber thickness is increased to improve spectral responsivity, then the absorption efficiency increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of increasing absorber thickness in the vertical dimension, the patent extends the absorption path laterally through the optical coupling layer. The optical couplers guide light laterally through the absorber region, effectively increasing the absorption length without increasing device thickness or complexity. This lateral expansion approach maintains simple device architecture while improving spectral responsivity.
Solution Approach 2:
The optical coupling layer serves as an intermediary structure that facilitates extended light absorption. The optical couplers within this layer act as mediators that redirect and guide light laterally through the absorber material, enabling increased absorption efficiency without requiring thicker absorbers or more complex device structures.
3Device complexity
If conventional vertical photodiode structure is used, then the device structure is simple, but the signal-to-noise ratio in infrared range is reduced
Solution Approach 1:
The patent changes the absorption geometry from vertical to lateral by introducing optical couplers in the optical coupling layer. This lateral absorption path increases the effective absorption length for infrared wavelengths, thereby improving the signal strength and signal-to-noise ratio while maintaining relatively simple device structure.
Solution Approach 2:
The patent modifies the optical path parameters by introducing optical couplers that change the direction and length of light propagation through the absorber. This parameter change extends the absorption path length specifically for infrared wavelengths, enhancing signal detection capability and improving signal-to-noise ratio without significantly increasing device 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
The solution significantly increases signal-to-noise ratio in the infrared and near-infrared ranges, surpassing the limitations of conventional vertically stacked photodiodes by extending absorption up to 1250 nm or more.
Implementation Method 1
The optical coupler allows for deflecting incident light towards the first lateral absorber region
Implementation Method 2
The first lateral absorber region comprises an absorber material with a bandgap, e.g. in the infrared, IR, or in the near infrared, NIR
Implementation Method 3
The first lateral absorber region comprises an absorber material with a bandgap, e.g. in the infrared, IR, or in the near infrared, NIR
Data Source
AI summary
A semiconductor device for infrared detection comprises a stack of a first semiconductor layer, a second semiconductor layer and an optical coupling layer. The first semiconductor layer has a first type of conductivity and the second semiconductor layer has a second type of conductivity. The optical coupling layer comprises an optical coupler and at least a first lateral absorber region. The optical coupler is configured to deflect incident light towards the first lateral absorber region. The first lateral absorber region comprises an absorber material with a bandgap Eg in the infrared, IR.