Germanium Photodetector Structure for Low Dark Current
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Solution Overview
Problem
Existing photodetectors face challenges in achieving low dark current and high quantum efficiency simultaneously due to the limitations in doping concentration ratios and material compatibility at heterointerfaces, which affect signal-to-noise ratio and sensitivity.
Innovation Solution
The photo-detecting apparatus employs a structure with distinct doping concentrations and materials between the absorption region and the carrier conducting layer, forming heterointerfaces with specific doping concentration ratios to minimize dark current and enhance quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the doping concentration in the absorption region is increased to improve quantum efficiency, then the quantum efficiency is improved, but the dark current increases
Solution Approach 1:
The patent applies local quality by creating distinct doping concentration zones: the absorption region has high doping concentration (≥1×10^16 cm^-3) to maximize quantum efficiency, while the carrier conducting layer has low doping concentration (≤1×10^15 cm^-3) to minimize dark current. This spatial differentiation of doping concentrations allows each region to optimize its local function without compromising the other.
Solution Approach 2:
The patent employs composite material structure by forming a heterointerface between the absorption region and carrier conducting layer made of different semiconductor materials (e.g., Ge/Si, Ge/SiGe). This material composition difference creates a type-I band alignment that forms energy barriers, enabling the system to simultaneously achieve high carrier generation efficiency in the absorption region and low dark current in the carrier conducting layer.
2Object-generated harmful factors
If heterointerfaces with large doping concentration ratios are used to reduce dark current, then dark current is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent implements parameter changes by precisely controlling the doping concentration ratio between the absorption region and carrier conducting layer to be at least 10:1. This parameter optimization achieves effective dark current suppression while maintaining manufacturability through standard semiconductor fabrication processes.
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 proposed structure achieves low dark current and high quantum efficiency by optimizing doping concentrations and material differences at heterointerfaces, improving signal-to-noise ratio and sensitivity.
Implementation Method 1
an absorption region in contact with the carrier conducting layer and configured to receive an optical signal and to generate photo-carriers in response to the optical signal
Data Source
AI summary
An optical sensing apparatus is provided. The optical sensing apparatus includes a semiconductor substrate composed of a first material; a transmitter-receiver set supported by the semiconductor substrate and including: (1) a photodetector includes an absorption region composed of a second material including germanium and configured to receive an optical signal and to generate photo-carriers in response to the optical signal; and (2) a light source including a light-emitting region composed of a third material including germanium and configured to emit a light toward a target; wherein the absorption region includes at least a property different from a property of the light-emitting region, wherein the property includes strain, conductivity type, peak doping concentration, or a ratio of the peak doping concentration to a peak doping concentration of the semiconductor substrate; wherein the first material is different from the second material and the third material.