Negative photoconductivity in crystals, particularly in 2D layered materials like graphene-phosphorene hybrid structures, can significantly impact the generation of terahertz (THz) radiation.
When a crystal is exposed to THz radiation, the conductivity of the crystal changes due to the carrier heating by the incident radiation absorbed in the graphene layer. This heating leads to the relocation of a significant fraction of the carriers into the phosphorene layer. Due to the relatively low mobility of the carriers in the phosphorene layer, their main role is associated with a substantial reinforcement of the scattering of the carriers.
A strong negative conductivity of the graphene-phosphorene channel can provide much higher responsivity of the THz hot-carriers and bolometric photodetectors in comparison with the bolometers with solely the graphene channels. This means that negative photoconductivity can enhance the detection of THz radiation.
Moreover, an increase in THz transmission after excitation corresponds to a decrease in photo-induced conductivity while a decrease in transmission indicates increased conductivity. This principle is used in hot-carrier bolometers exhibiting negative or positive photoconductivity. In summary, negative photoconductivity can influence generation and detection.
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Negative photoconductivity in crystals can have implications for the generation of radiation, particularly in the terahertz (THz) frequency range. Photoconductivity refers to the increase in electrical conductivity of a material when illuminated. In the case of negative photoconductivity, the conductivity decreases upon exposure to light. Understanding how negative photoconductivity affects the generation of terahertz radiation involves considering the material's properties and the specific mechanisms at play.
Terahertz Radiation Generation:
Terahertz radiation falls in the electromagnetic spectrum between microwave and infrared frequencies, roughly in the range of 0.1 to 10 terahertz. Various methods are employed to generate terahertz radiation, and one common approach involves using photoconductive antennas.
Negative Photoconductivity Impact:
If a crystal exhibits negative photoconductivity, it means that its conductivity decreases upon exposure to light. In the context of terahertz radiation generation, this characteristic can have several effects:
Research and Optimization:
Researchers working on terahertz radiation generation with photoconductive materials often engage in extensive studies to understand the specific photoconductivity characteristics of the chosen material. This involves exploring the material's response to different wavelengths, intensities, and durations of incident light.
Optimizing the crystal properties, doping levels, and experimental parameters can help mitigate the challenges associated with negative photoconductivity. Additionally, alternative materials with positive or enhanced photoconductivity may be explored to improve terahertz radiation generation efficiency.
In summary, while negative photoconductivity may present challenges in terahertz radiation generation, researchers can address these challenges through careful material selection, optimization, and an understanding of the specific impact of negative photoconductivity on the generated radiation.
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