Buried-Waveguide Light Receiving Element Reducing Dark Current
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Solution Overview
Problem
Conventional buried-waveguide-type light receiving elements face challenges with high leak current and reduced high-speed response due to p-type dopant diffusion in the Fe-doped InP layer, leading to increased dark current and reduced optical input resistance.
Innovation Solution
Incorporating a first semiconductor layer with an impurity concentration of 1×10^17 cm^-3 or less between the n-type light guide layer and the light absorption layer, embedded in a Fe-doped insulating material layer, to increase the depletion layer and reduce dark current, while maintaining high sensitivity and high-speed operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional buried-waveguide-type light receiving element uses a Fe-doped InP layer to embed the waveguide, then optical confinement is improved, but p-type dopant diffusion occurs causing high leak current and reduced reliability
Solution Approach 1:
An undoped or low-impurity semiconductor layer is introduced as an intermediary barrier between the p-type light guide layer and the light absorption layer. This intermediate layer prevents p-type dopant diffusion into the absorption layer while maintaining optical confinement through the Fe-doped InP burial layer, thereby reducing leak current without sacrificing optical performance.
Solution Approach 2:
The light guide layer is segmented into a p-type light guide layer and an adjacent undoped or low-impurity semiconductor layer. This segmentation creates a functional division where the p-type layer provides optical confinement and the undoped layer acts as a diffusion barrier, preventing dopant migration to the absorption layer.
2Measurement precision
If the waveguide length is increased to improve sensitivity, then photoelectric conversion efficiency is improved, but high-speed response performance deteriorates
Solution Approach 1:
The invention optimizes the impurity concentration parameter of the semiconductor layer adjacent to the light absorption layer, setting it at undoped or 1×10^17 cm^-3 or less. This parameter change creates an optimal balance between depletion layer width (affecting sensitivity) and carrier transit time (affecting response speed), achieving both high sensitivity and high-speed response.
3Loss of energy
If a non-semiconductor material film is deposited to improve optical confinement, then radiation loss is reduced, but recombination levels occur at the interface causing degradation
Solution Approach 1:
The invention uses a semiconductor material with the same composition as the light absorption layer for the undoped or low-impurity layer adjacent to it. This homogeneous material choice eliminates interface recombination levels and prevents degradation, while the Fe-doped InP burial layer provides the necessary optical confinement through refractive index difference.
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 effectively reduces leak current, enhances sensitivity, and maintains high-speed performance, achieving a high signal-to-noise ratio and power efficiency for the light receiving element.
Implementation Method 1
a Fe-doped insulating material layer located on the semiconductor substrate and embedding side walls of the waveguide layer
Implementation Method 2
light is caused to enter a guide layer transparent to incident light on the cleaved end face and is guided to a photoelectric conversion section (light absorption layer)
Data Source
AI summary
A buried-waveguide light detecting element includes an n-type cladding layer on a Fe-InP substrate, a waveguide on a portion of the n-type cladding layer, and in which an n-type light guide layer, an i-light guide layer having a refractive index equal to or higher than that of the n-type cladding layer and undoped or having an impurity concentration of 1×1017 cm−3 or less, lower than the impurity concentration in the n-type light guide layer, a light absorption layer having a refractive index higher than that of the i-light guide layer, a p-type light guide layer, and a p-type cladding layer are successively layered in mesa form, from the Fe—InP substrate, and a blocking layer on the Fe—InP substrate and in which side walls of the waveguide are embedded.