SiGe Trench Photodetector Absorption Depth
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Solution Overview
Problem
Current near-infrared photodetector semiconductor devices face limitations in absorption depth and light sensitivity due to critical thickness constraints of SiGe layers, and there is a need for improved monolithic integration of optics and electronics for enhanced performance and smaller size.
Innovation Solution
The proposed solution involves a near-infrared photodetector semiconductor device with trenches in the semiconductor layer, where a doped SiGe alloy layer is epitaxially grown on silicon, and a polysilicon layer is added, allowing for increased absorption length and sensitivity by varying the germanium content and using conductive filling materials to enhance photocarrier collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a SiGe layer is used to extend absorption depth in near-infrared photodetectors, then absorption length is improved, but the depth is limited by the critical thickness of the SiGe layer
Solution Approach 1:
The patent transitions from vertical growth limitation to lateral growth by etching trenches into the substrate and filling them with SiGe material. This dimensional change from vertical stacking to lateral expansion allows the absorption region to extend deeper into the substrate without being constrained by the critical thickness of epitaxial SiGe layers, thereby achieving greater absorption depth while maintaining manufacturing feasibility
2Illumination intensity
If the trench depth is increased to improve absorption, then light sensitivity is improved, but the trench sidewalls become rough
Solution Approach 1:
The patent applies a preliminary action by depositing a sacrificial layer into the trenches before etching. This sacrificial layer serves as a template that guides the etching process to create smooth sidewalls. After the SiGe material is deposited conformally on these smooth sidewalls, the sacrificial layer is removed, leaving behind trenches with smooth surfaces that enable effective light absorption without the sidewall roughness that would otherwise limit sensitivity
3Volume of moving object
If monolithic integration of optics and electronics is implemented, then device size is reduced and performance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent merges the optical detection function with electronic processing by integrating the SiGe photodetector trench structure directly with underlying electronic circuits on the same semiconductor substrate. The trenches are formed and filled with photodetector materials in the same manufacturing sequence as the electronic components, creating a monolithic device where optics and electronics are combined in a single integrated structure, reducing overall device size and interconnect 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 enhances light sensitivity in the near-infrared range by increasing absorption length and improving photocarrier collection efficiency, enabling more effective photodetection in red and near-infrared light spectral ranges.
Implementation Method 1
a SiGe alloy layer which is epitaxially grown on the silicon
Implementation Method 2
The SiGe alloy layer is doped for the second type of conductivity... improving photocarrier collection efficiency... light sensitivity in the near-infrared range
Data Source
Figure 1~4
Figure 5~7
AI summary
The near-infrared photodetector semiconductor device comprises a semiconductor layer (1) of a first type of conductivity with a main surface (10), a trench or a plurality of trenches (2) in the semiconductor layer at the main surface, a SiGe alloy layer (3) in the trench or the plurality of trenches, and an electrically conductive filling material of a second type of conductivity in the trench or the plurality of trenches, the second type of conductivity being opposite to the first type of conductivity.