Graphene Photodetector Broadband Detection Dark Current Reduction
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Solution Overview
Problem
Current photodetectors using semiconductor materials have limitations such as band gap restrictions and limited bandwidth, leading to suboptimal performance in detecting photons across various wavelengths and requiring external biases that can introduce dark current.
Innovation Solution
A photodetector design utilizing single or multi-layer graphene as the photoconducting layer, which allows for the detection of photons across any wavelength due to its zero or small band gap and high carrier transport velocity, enabling the creation of a universal photodetector with enhanced bandwidth and reduced dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If semiconductor materials are used as photodetection material, then the photodetector can detect photons with energy greater than the band gap, but photons with energy less than the band gap cannot be detected and the bandwidth is limited by carrier transit time
Solution Approach 1:
The patent changes the fundamental material parameter from semiconductor with finite band gap to graphene with zero or very small band gap. This parameter change enables the photodetector to detect photons across a much broader wavelength range from ultraviolet to far-infrared, resolving the contradiction between wavelength range and detection efficiency by eliminating the band gap energy threshold that previously limited both range and efficiency.
Solution Approach 2:
The patent employs a composite structure combining graphene with semiconductor materials (such as SiGe, InGaAs, or InP) in a heterostructure configuration. The graphene layer serves as the photodetection region while the semiconductor provides carrier separation and collection. This composite approach leverages the broad spectral response of graphene while maintaining efficient carrier collection through the semiconductor, thus achieving both wide wavelength detection and high detection efficiency simultaneously.
2Reliability
If external biases are applied to semiconductor photodetectors to improve performance, then detection capability is enhanced, but dark current increases
Solution Approach 1:
The patent changes the material parameter from semiconductor to graphene, which has linear energy-momentum dispersion and zero or very small band gap. This enables the photodetector to operate with reduced or eliminated external bias while maintaining high detection capability. The unique electronic structure of graphene allows for high carrier mobility and efficient photoresponse without requiring high bias voltages that would generate significant dark current in semiconductor devices.
Solution Approach 2:
The patent converts the typically harmful dark current in semiconductor photodetectors into a beneficial low-noise operation by using graphene's unique properties. The zero or very small band gap of graphene, which in semiconductors would cause high thermal excitation and dark current, actually enables high photoresponse with minimal dark current in the graphene-based device, turning what would be a disadvantage into an advantage.
3Productivity
If semiconductor based photodetectors are used, then the device structure is well-established, but the intrinsic bandwidth is limited by carrier transit time in the photodetection region
Solution Approach 1:
The patent changes the material from semiconductor to graphene, which has extremely high carrier mobility and short carrier transit time. This parameter change directly increases the intrinsic bandwidth of the photodetector while maintaining a relatively simple device structure. The high carrier velocity in graphene allows for faster response times and higher bandwidth operation without requiring complex device architectures.
Solution Approach 2:
The patent creates a universal photodetector platform using graphene that can function across multiple wavelength ranges and application scenarios. The graphene-based photodetector can be configured for different wavelengths (UV, visible, infrared) and applications (imaging, communication, sensing) without fundamentally changing the device structure, achieving multi-functionality while maintaining high bandwidth performance.
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 graphene-based photodetector achieves efficient detection of photons across a wide range of wavelengths from ultraviolet to far-infrared with high bandwidth and minimal dark current, suitable for applications like imaging and remote sensing.
Implementation Method 1
Because of graphene's unique property of being a zero or very small band gap material, photons at any wavelength (or any energy level) can be absorbed
Implementation Method 2
The internal field is generated by applying a gate voltage to create a graphene p-n junction
Data Source
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AI summary
A photodetector which uses single or multi-layer graphene on a gate oxide layer (12) as the photon detecting layer (14) is disclosed. Multiple embodiments are disclosed with different configurations of the source (8), drain (6) and gate (10) electrodes. In addition, a photodetector array comprising multiple photodetecting elements is disclosed for applications such as imaging and monitoring. An optical waveguide underlying the graphene layer (14) may be embedded into substrate (10) or gate oxide layer (12) in order to channel photons towards graphene layer (14).