Surface-Junction UV Photodetector Using 2D Material Interface
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional silicon photodetectors are inefficient for detecting ultraviolet (UV) light due to the location of the space charge region, which results in a low probability of UV light reaching the p-n junction.
Innovation Solution
A photodetector is designed with a semiconductor and a two-dimensional (2D) material, such as graphene, where the space charge region is located directly at the surface of the semiconductor, enhancing the detection efficiency of UV light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the p-n junction is buried in the semiconductor material, then the photodetector can detect infrared light effectively, but UV light detection efficiency is poor because UV light is absorbed at the surface and cannot reach the p-n junction
Solution Approach 1:
Instead of having the space charge region buried deep in the semiconductor as in conventional photodetectors, this invention inverts the structure by positioning the space charge region directly at the semiconductor surface. This is achieved by forming a Schottky contact between a metal layer and the lightly-doped drift region, creating a metal-semiconductor junction at the surface where UV light enters, thereby directly exposing the space charge region to incident UV photons.
Solution Approach 2:
The invention transitions from a conventional bulk buried junction architecture to a surface-based Schottky junction architecture. By moving the space charge region from the interior (three-dimensional bulk) to the surface (two-dimensional interface), the design exploits the surface dimension to capture UV light before it penetrates deeply into the semiconductor, effectively utilizing the surface as the active detection region.
2Reliability
If conventional silicon photodetectors are used, then manufacturing is straightforward, but UV light detection efficiency is low due to surface absorption
Solution Approach 1:
The photodetector structure is segmented into distinct functional layers: a heavily-doped semiconductor substrate, a lightly-doped drift region, a metal layer forming the Schottky contact, and an intermediate layer. This segmentation allows each layer to be optimized for its specific function while maintaining compatibility with standard semiconductor fabrication processes, making the enhanced UV detection capability achievable through modular manufacturing.
Solution Approach 2:
The invention changes key structural parameters: the doping concentration gradient (heavily-doped substrate to lightly-doped drift region), the junction location (surface Schottky contact instead of buried junction), and the metal layer thickness (optimized to form proper Schottky contact). These parameter changes enable UV light to reach the space charge region while maintaining ease of manufacture through controlled doping profiles and standard thin-film deposition techniques.
3Reliability
If the space charge region is positioned deeper in the material, then infrared light detection is improved, but UV light detection efficiency decreases
Solution Approach 1:
The invention applies local quality by creating a specialized Schottky contact structure at the surface region where UV light enters, while the bulk substrate maintains its conventional heavily-doped structure. The lightly-doped drift region provides a transition zone that allows the space charge region to be localized at the surface without compromising the overall device structure, enabling UV-specific optimization while maintaining infrared detection capability.
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 proposed photodetector achieves improved UV detection efficiency, with 30% or greater photocurrent at 400 nm illumination and 100% or greater photocurrent at 260 nm illumination, compared to conventional silicon photodetectors.
Implementation Method 1
Silicon photodetectors are devices that convert light into electrical signals... an electron-hole pair generated by the photon can contribute to a photocurrent
Data Source
AI summary
A photodetector and method of making the same including a semiconductor and a 2D material. The space charge region is located directly at the surface of the semiconductor. A photon with a small wavelength, once it enters the semiconductor, is immediately inside the space charge region in which an electron-hole pair generated by the photon can contribute to a photocurrent. This makes the photodetector an efficient UV detector. Interdigitated oxide structures between the semiconductor and the 2D material further enhance the sensitivity of the photodetector to, for example, UV light.