Photovoltage Field-Effect Transistor Infrared Detection
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Solution Overview
Problem
Silicon photodetectors are limited by their bandgap, preventing effective detection of infrared radiation beyond 1100 nm, and existing solutions like black silicon and colloidal quantum dots face challenges with responsivity and integration with silicon.
Innovation Solution
A photovoltage field effect transistor (PVFET) using a silicon transport channel with a sensitizing medium, such as colloidal quantum dots, that modulates conductivity in response to electromagnetic radiation, enabling detection beyond silicon's bandgap with high responsivity and fast response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon photodetectors are used for infrared detection, then the device can be fabricated with standard silicon processes, but detection is limited to wavelengths shorter than 1100 nm due to silicon's bandgap
Solution Approach 1:
The patent creates a composite structure combining silicon transport channel with colloidal quantum dot sensitizing medium. The quantum dots absorb infrared radiation and transfer excitons to the silicon channel, enabling IR detection while maintaining silicon fabrication compatibility. This composite approach allows the device to detect wavelengths beyond pure silicon's bandgap limitation.
Solution Approach 2:
The colloidal quantum dots act as an intermediary between infrared radiation and the silicon transport channel. They absorb photons with wavelengths beyond silicon's bandgap and transfer the energy to silicon, mediating the detection process and overcoming the direct bandgap limitation of silicon.
2Device complexity
If black silicon is used for infrared detection, then the device structure is simple, but responsivity at infrared wavelengths is low (10^-2-10^-1 A/W)
Solution Approach 1:
The patent combines the simplicity of black silicon structure with the high infrared absorption capability of colloidal quantum dots. The quantum dot sensitizing medium is deposited on the black silicon surface, creating a composite that maintains structural simplicity while dramatically improving responsivity through enhanced infrared absorption and exciton transfer.
3Adaptability or versatility
If colloidal quantum dots are used in traditional photoFET, then infrared sensitivity is achieved, but modest transport in the quantum dot solid limits device performance
Solution Approach 1:
The patent segments the device into distinct functional regions: a colloidal quantum dot sensitizing medium layer for infrared absorption and a separate silicon transport channel for efficient charge transport. This segmentation allows each material to optimize its function - quantum dots for IR sensitivity and silicon for high mobility charge transport - overcoming the limitation of modest transport in quantum dot solids.
4Speed
If photodetectors rely on the photoconductive effect, then they can achieve fast response time, but responsivity is reduced, or vice versa
Solution Approach 1:
The colloidal quantum dots serve as an intermediary that enables both high responsivity and fast response. They absorb infrared photons and generate excitons that are rapidly transferred to the silicon channel, where high mobility carriers provide fast response. The intermediary quantum dot layer decouples the absorption function from the transport function, allowing optimization of both responsivity and speed.
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 PVFET achieves a 5-order magnitude higher responsivity at 1500 nm and fast time response, overcoming the limitations of traditional silicon photodetectors and demonstrating efficient infrared detection using a room temperature solution process without requiring high temperature epitaxial growth.
Implementation Method 1
a sensitizing medium for receiving incident electromagnetic radiation and generating bound photocharges
Implementation Method 2
A transport channel adjacent to the sensitizing medium is adapted to change at least one electrical property when photocharges are generated in the sensitizing medium
Data Source
AI summary
In an embodiment, a photodetector is provided that provides a sensitizing medium adapted to receive electromagnetic radiation creating a junction with a transport channel, wherein the transport channel is adapted to exhibit a change in conductivity in response to reception of electromagnetic radiation by the sensitizing medium.