Digital Alloy Layers for Symmetric Optical Distribution in APDs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Waveguide type avalanche photodiodes (APDs) face challenges in achieving high light-receiving sensitivity and high-speed response due to asymmetric optical distribution and increased noise, primarily because of the use of conventional semiconductor materials with high refractive indices that lead to inefficient light confinement and thermal conductivity issues.
Innovation Solution
The semiconductor light-receiving device employs a digital alloy structure for at least one of the n-type buffer layer, multiplication layer, and p-type electric field control layer, which reduces the refractive index and enhances light confinement, thereby improving light-receiving sensitivity and high-speed response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional semiconductor materials with high refractive indices (InAlAs, InAlGaAs) are used for the electric field control layer and multiplication layer, then light-receiving sensitivity can be improved through efficient light confinement, but asymmetric optical distribution occurs and thermal conductivity deteriorates
Solution Approach 1:
The patent changes the refractive index parameter of the multiplication layer and electric field control layer by using digital alloy structures (InAs/InP superlattices) instead of conventional InAlAs or InAlGaAs materials. This parameter change reduces the refractive index difference between layers, achieving symmetrical optical distribution while maintaining efficient light confinement in the light absorption layer.
Solution Approach 2:
The patent employs composite material structures - specifically digital alloy structures composed of alternating InAs and InP layers - to replace conventional single-phase semiconductor materials. This composite approach enables simultaneous optimization of optical properties (refractive index matching for symmetry) and electrical properties (carrier multiplication efficiency) that cannot be achieved with conventional materials alone.
2Measurement precision
If InAlAs is used for the multiplication layer to increase ionization rate difference between electrons and holes, then light-receiving sensitivity increases, but refractive index increases causing asymmetric optical distribution and reduced light confinement in the absorption layer
Solution Approach 1:
The patent changes the refractive index parameter of the multiplication layer by using digital alloy structures with lower effective refractive indices compared to InAlAs. This enables symmetrical optical distribution and improved light confinement in the light absorption layer while maintaining the high ionization rate difference between electrons and holes through appropriate layer design and composition control.
3Speed
If the light absorption layer is thinned to achieve high-speed response, then response time improves, but light-receiving sensitivity decreases due to insufficient light absorption
Solution Approach 1:
The patent applies local quality optimization by creating symmetrical optical distribution through refractive index matching in the multiplication layer and electric field control layer. This symmetry concentrates light confinement precisely in the light absorption layer, enabling thin-layer design with sufficient light absorption for high sensitivity while maintaining short carrier transit paths for high-speed response.
4Use of energy by moving object
If digital alloy structure is used to reduce refractive index and achieve symmetrical optical distribution, then light confinement in absorption layer improves, but device complexity increases due to complex layer structure
Solution Approach 1:
The patent uses segmentation by dividing the multiplication layer and electric field control layer into alternating thin layers of InAs and InP (digital alloy structure). This segmentation creates the desired low effective refractive index and symmetrical optical distribution while using simple binary material systems that are easier to fabricate than complex ternary or quaternary alloys like InAlAs or InAlGaAs.
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 digital alloy structure achieves symmetrical optical distribution, increasing light confinement in the absorption layer, reducing noise, and enhancing the SN ratio, leading to improved light-receiving sensitivity and high-speed response.
Implementation Method 1
any one, any two, or three of the n-type buffer layer, the multiplication layer, and the p-type electric field control layer are composed of a digital alloy structure... reduces the refractive index and enhances light confinement
Implementation Method 2
A high electric field of about 800 kV/cm is applied to the multiplication layer to multiply (ionize) holes and electrons which are generated in the light absorption layer
Implementation Method 3
light absorption layer (InGaAs)... holes and electrons which are generated in the light absorption layer
Data Source
AI summary
A semiconductor light-receiving device (100) of the present disclosure includes: a semiconductor substrate (1); an n-type buffer layer (2) formed above the semiconductor substrate (1); a multiplication layer (3) formed above the n-type buffer layer (2); a p-type electric field control layer (4) formed above the multiplication layer (3); and a light absorption layer (5) formed above the p-type electric field control layer (4), wherein any one, any two, or three of the n-type buffer layer (2), the multiplication layer (3), and the p-type electric field control layer (4) are composed of a digital alloy structure.