Light Receiving Element With Inclined Substrate for Low-Polarization Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor light receiving elements face challenges in achieving both high sensitivity and high-speed response due to polarization dependency and limited optical path length, particularly when handling various polarized waves in intensity modulation direct detection methods.
Innovation Solution
A light receiving element is designed with a slope on the substrate that is neither perpendicular nor parallel to the substrate plane, allowing incident light to enter perpendicularly and interact with the light absorbing layer obliquely, utilizing a non-birefringent antireflective film to minimize polarization dependency and extend the optical path length, while using a metal electrode as a reflective film and a semi-insulating substrate to enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the light absorbing layer is increased to extend the optical path length, then sensitivity is improved, but carrier traveling time increases which hinders high-speed response
Solution Approach 1:
The invention introduces an inclined surface on the substrate that causes light to enter the light absorbing layer at an oblique angle rather than perpendicularly. This dimensional change in light propagation direction extends the optical path length within the same physical thickness of the light absorbing layer, thereby increasing sensitivity without increasing carrier traveling time and maintaining high-speed response capability
2Measurement precision
If a return structure is formed to extend the optical path length, then sensitivity is improved, but the structure complexity increases and light must enter from the back surface
Solution Approach 1:
Instead of forming a complex return structure that requires light to enter from the back surface, the invention uses a simple inclined surface on the front surface substrate. This inclined surface redirects light at an oblique angle to extend the optical path length, achieving enhanced sensitivity with minimal structural modification and without requiring back-surface light entry
3Measurement precision
If light enters obliquely with respect to the substrate plane to extend the optical path length, then sensitivity is improved, but polarization dependency increases which degrades reception characteristics
Solution Approach 1:
The inclined surface is configured with a specific orientation relationship to the light receiving direction such that light entering perpendicularly to the inclined surface becomes oblique to the light absorbing layer. This geometric configuration extends the optical path length while the anti-reflective film on the inclined surface minimizes polarization-dependent reflection, thereby reducing polarization dependency and maintaining good reception characteristics for various polarized waves
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 reduces polarization dependency and increases the optical path length, resulting in improved light receiving characteristics and sensitivity, enabling efficient handling of various polarized waves without compromising high-speed response.
Implementation Method 1
A photodiode is an element that performs photoelectric exchange by generating electrons and holes when light is absorbed through irradiation with light having an energy equal to or higher than the bandgap of a semiconductor
Implementation Method 2
a first electrode that is formed in contact with the second semiconductor layer, is formed with a metal, and functions as a reflective film
Data Source
AI summary
In a light receiving element, a first semiconductor layer that is formed on the upper surface of a substrate and is formed with a semiconductor of a first conductivity type, a light absorbing layer formed with a semiconductor, a second semiconductor layer formed with a semiconductor of a second conductivity type, a first electrode that is formed in contact with the second semiconductor layer, is formed with a metal, and functions as a reflective film, and a second electrode formed on the first semiconductor layer are formed in a vertical direction on the upper surface of the substrate. In the light receiving element, a slope that is neither perpendicular nor parallel to the substrate plane is formed on the substrate, and incident light that has perpendicularly entered the slope is made to enter the light absorbing layer obliquely with respect to the vertical direction.