Multilayer Photoconductor Doping for Low Dark Current THz Response
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Solution Overview
Problem
Existing photoconductors lack optimization in their photoconductive properties, particularly in the terahertz range, leading to inefficiencies in electromagnetic radiation reception and transmission.
Innovation Solution
A photoconductor with a layer package comprising multiple sub-packages of differently doped semiconductor layers, where one layer has a high dopant concentration for recombination centers and the other has low conductivity to reduce dark currents, optimized in thickness and dopant distribution to enhance electron mobility and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor layers are uniformly doped, then the manufacturing process is simple, but the photoconductive properties cannot be individually optimized
Solution Approach 1:
The patent applies local quality by creating different doping configurations in different regions of the semiconductor layers. Specifically, it uses a superlattice structure with alternating high-doping and low-doping layers, where each layer has tailored doping concentrations and distributions to perform specific functions (recombination centers in high-doping layers, dark current reduction in low-doping layers), thereby optimizing photoconductive properties through spatially varying material characteristics.
2Reliability
If the first semiconductor layer has high dopant concentration for recombination centers, then electron-hole recombination is enhanced, but dark currents increase
Solution Approach 1:
The patent segments the semiconductor structure into multiple alternating layers with different doping characteristics. The high-doping layers provide recombination centers while the low-doping layers act as barriers to dark currents. This segmentation allows the system to simultaneously achieve high recombination rates and low dark currents by distributing different functions across separate layers rather than requiring a uniform structure.
Solution Approach 2:
The low-doping layers serve as intermediary elements between the high-doping layers. These intermediary layers with lower dopant concentrations and more homogeneous distributions act as buffers that prevent dark current generation while allowing the high-doping layers to perform their recombination function, thus mediating between the conflicting requirements of high recombination and low dark current.
3Speed
If the semiconductor layers are made thinner to improve terahertz response, then the photoconductive speed increases, but the electrical resistance increases
Solution Approach 1:
The patent employs a composite material structure consisting of alternating high-doping and low-doping semiconductor layers forming a superlattice. This composite structure combines the benefits of thin layers (fast photoconductive response) with the advantages of optimized doping profiles (controlled electrical resistance). The alternating layers create a material system where charge carrier transport and recombination are enhanced while maintaining appropriate resistance levels.
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 enables efficient conversion of optical radiation into electron-hole pairs, high electron mobility, short electron lifetime, and high resistance, effectively compensating for dark currents and improving overall photoconductive performance.
Implementation Method 1
Photoconductors can be used, for example, in combination with suitable antennas for receiving and/or transmitting electromagnetic radiation in the terahertz range
Implementation Method 2
the dopant in the first photoconductive semiconductor layer forms a higher concentration of dopant clusters than in the second photoconductive semiconductor layer
Implementation Method 3
the second photoconductive semiconductor layer has a greater electrical resistance than the first photoconductive semiconductor layer
Implementation Method 4
an intermediate layer is arranged between the first and second semiconductor layer, which slows down the diffusion of the dopant from the first into the second semiconductor layer
Implementation Method 5
The thickness of the first and second photoconductive semiconductor layer in each sub-package is preferably on the order of magnitude of the de-Broglie wavelength of electrons that are located in the respective semiconductor layer
Data Source
AI summary
The invention relates inter alia to a photoconductor (10) comprising a multilayer (13) which comprises a plurality of photoconductive semiconductor layers (131-134). According to the invention, the multilayer (13) comprises at least two sublayers (130) which each comprise at least a first photoconductive semiconductor layer (131) and a second photoconductive semiconductor layer (132), wherein the first and the second photoconductive semiconductor layer (131, 132) are doped to different degrees for each of the sublayers (130).