Undoped Single-Crystal Photoconductor for RF Energy Modulation
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Solution Overview
Problem
Conventional photoconductive semiconductor materials have defects that lead to rapid recombination of electron-hole pairs, reducing the number of free charges available for reflecting or absorbing radio-frequency (RF) energy, resulting in lower efficiency in RF energy reflection or absorption.
Innovation Solution
A photoconductive semiconductor device using an undoped and single-crystal semiconductor material with electrodes arranged normal to the substrate and a power supply to apply a voltage, increasing the lifetime of electron-hole pairs and modulating electromagnetic energy reflection or absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photoconductive semiconductor materials are used, then the device can generate electrical conductivity when illuminated, but the materials have defects that cause rapid recombination of electron-hole pairs, reducing the number of free charges available for RF energy reflection or absorption
Solution Approach 1:
The patent changes the material parameter from amorphous to single-crystal structure, which fundamentally alters the recombination characteristics. Single-crystal materials have fewer defects and dislocations compared to amorphous materials, thereby extending carrier lifetime while maintaining or improving RF energy interaction efficiency
Solution Approach 2:
The patent employs a composite structure combining single-crystal semiconductor material with specific electrode configurations and interface designs. This composite approach optimizes both carrier lifetime and RF energy reflection/absorption by integrating materials with complementary properties
2Ease of manufacture
If amorphous semiconductor materials are used, then the device structure can be simpler to manufacture, but the materials have poor carrier mobility which negatively impacts conductivity and limits usefulness for reflecting or absorbing RF energy
Solution Approach 1:
The patent changes the structural parameter from amorphous to single-crystal form, which dramatically improves carrier mobility despite the potentially more complex manufacturing process. The crystalline structure provides well-defined electron pathways and reduces scattering centers
3Device complexity
If free electrons and holes are kept in proximity in traditional photoconductor devices, then the device structure is simpler, but rapid recombination occurs which lowers the average number of free charges available for use as RF reflectors or absorbers
Solution Approach 1:
The patent segments the photoconductor into functionally distinct regions including charge generation zones, charge separation zones, and charge collection zones. This spatial segmentation prevents rapid recombination by separating electron-hole pairs into different regions while maintaining overall structural organization
Solution Approach 2:
The patent introduces vertical dimensionality through layered structures and depth-controlled illumination. By utilizing the third dimension (depth), the device creates extended charge collection paths and separates charge carriers in the vertical direction, reducing recombination while maintaining a relatively simple planar footprint
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 significantly increases the carrier lifetime and electrical conductivity, enhancing the device's ability to reflect or absorb RF energy, leading to improved efficiency compared to conventional photoconductor structures.
Implementation Method 1
A photoconductive semiconductor material has an electronic band structure that is determined by the crystal properties of the material. When a semiconductor material is illuminated by a light source, such as a laser, electrons in the material are able to absorb energy enabling them to transition from the valence band to the conduction band.
Implementation Method 2
a power supply for applying a voltage to the electrodes. Using the electrodes is advantageous in enabling the electron-hole pairs formed by illumination of the substrate to be pulled apart to different locations within the substrate
Implementation Method 3
A material with mobile charges can reflect or absorb radio frequency waves. Therefore, a photoconductor may be used to either reflect or absorb radio-frequency (RF) energy when illuminated by light
Data Source
AI summary
A photoconductor assembly includes a substrate formed of an undoped and single-crystal semiconductor material that is configured to absorb electromagnetic energy, a plurality of electrodes arranged normal to the substrate, and a power supply that applies a voltage to the electrodes for modulating the electromagnetic energy through the substrate.