Scatterer Photodetector Layout for High Sensitivity and Low Dark Current
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Solution Overview
Problem
Existing photodetectors face challenges in improving detection sensitivity while minimizing dark current, particularly in semiconductor light receiving elements using InGaAs substrates, due to the attenuation of localized non-uniform electric fields and the generation of dark current at Schottky junctions.
Innovation Solution
A photodetector design featuring a scatterer with a width equal to or less than the wavelength of incident light, forming a localized non-uniform electric field within the semiconductor light absorption layer, and separate extraction electrodes to enhance photocurrent extraction, while minimizing dark current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the position where the localized non-uniform electric field is generated is in the vicinity of the interface between the conductive layer and the second conductive type semiconductor layer, then the device structure is simplified, but the detection sensitivity is insufficient because the localized non-uniform electric field is far from the non-doped semiconductor light absorption layer
Solution Approach 1:
The patent introduces a third dimension (depth) by forming an opening that penetrates through the conductive layer and second conductive type semiconductor layer to reach the non-doped semiconductor light absorption layer. This vertical dimensional change allows the scatterer to be positioned at the optimal depth where it can generate localized non-uniform electric field directly in the light absorption layer, resolving the contradiction between structural simplicity and detection sensitivity.
Solution Approach 2:
The patent introduces a scatterer as an intermediary element that is embedded in the opening and extends into the non-doped semiconductor light absorption layer. This scatterer acts as a mediator that generates the localized non-uniform electric field precisely where needed in the light absorption layer, enabling effective coupling between the incident light and the semiconductor material while maintaining structural organization.
2Measurement precision
If the metal electrode is embedded in the semiconductor layer to improve detection sensitivity, then the wave number component of the localized non-uniform electric field is enhanced, but the dark current increases due to the Schottky junction
Solution Approach 1:
The patent extracts the light-receiving function from the metal electrode by removing the metal electrode from direct contact with the non-doped semiconductor light absorption layer. Instead, a scatterer (made of dielectric material or semiconductor with different refractive index) is placed in the opening to generate the localized non-uniform electric field. This separation takes out the harmful Schottky junction effect while preserving the beneficial electric field generation, thereby reducing dark current while maintaining detection sensitivity.
Solution Approach 2:
The patent creates a functional copy of the metal electrode's light-receiving capability using a scatterer made of dielectric material or semiconductor. This scatterer copy performs the essential function of generating localized non-uniform electric field through incident light, but without the harmful side effect of forming a Schottky junction with the semiconductor layer, thus eliminating dark current generation.
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 design improves detection sensitivity by effectively matching the position of the localized non-uniform electric field with the depletion layer, reduces dark current, and allows for high-speed photodetection with increased manufacturing yield and efficiency.
Implementation Method 1
a scatterer that is provided with a width equal to or less than a wavelength of incident light so as to be in contact with the semiconductor light absorption layer and forms a localized non-uniform electric field inside the semiconductor light absorption layer by scattering the incident light
Implementation Method 2
One of the effects of the localized non-uniform electric field is that a large wave number can be given to the electrons inside the semiconductor by the uncertainty principle. Therefore, even a semiconductor material having an indirect transition can directly perform an optical transition
Implementation Method 3
extracts a photocurrent generated in the semiconductor light absorption layer due to formation of the localized non-uniform electric field
Data Source
AI summary
A photodetector includes: a first conductive type semiconductor layer; a semiconductor light absorption layer provided on the first conductive type semiconductor layer; a scatterer that is provided with a width equal to or less than a wavelength of incident light so as to be in contact with the semiconductor light absorption layer and forms a localized non-uniform electric field inside the semiconductor light absorption layer by scattering the incident light; a second conductive type semiconductor layer provided on the semiconductor light absorption layer so as to be apart from the scatterer; and an extraction electrode that is provided on the second conductive type semiconductor layer so as to be apart from the scatterer and extracts a photocurrent generated in the semiconductor light absorption layer due to formation of the localized non-uniform electric field.