Silicon Schottky Photodiode Geometry for Near-Infrared Absorption
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Solution Overview
Problem
Current photodiodes are inefficient in detecting electromagnetic radiation with wavelengths between 1000 nm and 2500 nm due to limitations in semiconductor materials, leading to high costs and environmental concerns, and existing solutions like InGaAs and Schottky diodes suffer from low sensitivity and compatibility issues with silicon technology.
Innovation Solution
A silicon photodiode with a beam guiding unit featuring a two-stage geometry, where the cross-sectional area decreases more strongly in the second portion than in the first, guiding electromagnetic radiation to a Schottky junction for improved absorption, utilizing silicon technology to enhance sensitivity and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If InGaAs is used as detector material for wavelengths above 1100 nm, then sensitivity is improved, but manufacturing cost increases and compatibility with silicon technology is lost
Solution Approach 1:
The device is divided into two functional segments: a silicon substrate providing mechanical support and electrical functionality, and a separate metal layer providing optical absorption and internal photoemission. This segmentation allows each material to be optimized for its specific function while maintaining compatibility through standardized fabrication processes.
Solution Approach 2:
The invention creates a composite structure combining silicon and metal materials in a single device. The silicon substrate serves as the base material for fabrication, while metal layers (such as aluminum, copper, or gold) are deposited on top to provide the Schottky junction for infrared detection. This composite approach leverages the advantages of both materials: silicon's compatibility with existing technology and metal's optical properties for NIR detection.
2Ease of manufacture
If a planar metal-semiconductor junction is used, then manufacturing is simplified, but radiation absorption is reduced due to mirror reflection
Solution Approach 1:
The metal layer is designed with a curved or non-planar surface topology that replaces the flat mirror-like interface. This curvature modifies the optical path of incident radiation, reducing specular reflection and increasing the probability of photon absorption at the metal-semiconductor junction. The curved surface helps to trap light within the structure, enhancing absorption efficiency while maintaining a relatively simple manufacturing process through standard deposition techniques.
3Measurement precision
If surface roughness is increased to disperse radiation, then absorption is improved, but metalized surface area increases causing higher dark currents
Solution Approach 1:
The invention optimizes the surface parameters of the metal layer, specifically controlling the root mean square (RMS) roughness to be between 0.1 μm and 10 μm. This parameter optimization achieves a balance: sufficient surface scattering to enhance radiation absorption while limiting the increase in effective metalized surface area that would otherwise amplify dark currents. The controlled roughness creates optimal light-trapping conditions without excessive surface area expansion.
4Ease of manufacture
If silicon photodetectors operate on fundamental absorption, then manufacturing is compatible with silicon technology, but detection above 1100 nm becomes impossible
Solution Approach 1:
The metal layer acts as an intermediary that enables extended wavelength detection. While silicon alone cannot detect photons with wavelengths above 1100 nm due to its bandgap limitations, the metal layer provides an alternative detection mechanism through internal photoemission at the Schottky junction. This intermediary metal layer absorbs the higher-energy photons and generates charge carriers that can be collected by the silicon substrate, effectively extending the detection range while maintaining silicon technology compatibility.
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 solution enables efficient detection of electromagnetic radiation in the near-infrared range with improved sensitivity and reduced manufacturing complexity, overcoming the limitations of existing technologies by leveraging silicon technology and internal photoemission at the Schottky junction.
Implementation Method 1
The sidewalls of the beam guiding unit may be configured to guide electromagnetic radiation incident in the base area towards the metal material by means of total internal reflection
Implementation Method 2
The metal material may be configured to form, together with the second portion, a Schottky junction for absorbing electromagnetic radiation... incident radiation generates charge carriers at a metal-semiconductor junction
Data Source
AI summary
An apparatus for absorbing electromagnetic radiation, including: a substrate with a main side and a beam guiding unit arranged on the main side of the substrate, wherein the beam guiding unit includes a semiconductor material and wherein the semiconductor material is transparent for the electromagnetic radiation. The beam guiding unit includes a first and a second portion, wherein the first portion is arranged between the substrate and the second portion. A cross-sectional area of the beam guiding unit in parallel to the main side of the substrate decreases with increasing distance to the main side more strongly in the second portion than in the first portion. The apparatus also includes a metal material, wherein the metal material is arranged at the second portion of the beam guiding unit on a side of the second portion facing away from the substrate, the metal material providing a Schottky junction.