- The paper introduces a linear-dichroic BP photodetector that effectively spatially separates photo-generated carriers using a vertical p–n junction.
- The experimental design exploits BP’s anisotropic structure, enabling broadband photodetection from 400 nm to 3750 nm with significant responsivity enhancement under gate voltage.
- The integration of ARPES and ab initio calculations substantiates the observed optical anisotropy, paving the way for advanced polarization-sensitive optoelectronic applications.
Broadband Linear-Dichroic Photodetector in a Black Phosphorus Vertical p-n Junction
The paper details the development and characterization of a linear-dichroic broadband photodetector based on a vertical p-n junction in black phosphorus (BP). The authors successfully demonstrate the enhanced photodetection capabilities of BP due to its strong intrinsic linear dichroism. This property stems from BP's unique in-plane optical anisotropy with significant implications for future optoelectronic devices.
A pivotal aspect of the research is the use of BP's inherent anisotropic structure to achieve linear dichroism over an extensive spectral range from approximately 400 nm to 3750 nm. BP's puckered atomic structure, along with its rectangular in-plane lattice, results in a pronounced anisotropic conductive and optical property. This results in light being preferentially absorbed along one crystalline axis, thus enhancing BP's suitability for polarization-sensitive applications.
The paper utilizes a vertical p-n junction structure, where gating in the transistor geometry induces a perpendicular built-in electric field. This configuration spatially separates photo-generated electron-hole pairs, reducing their recombination rate and effectively boosting the photodetector's performance. Experimental measurements corroborate with theoretical predictions and reveal a substantial difference in photoconductance when light is polarized along the distinct axes of the BP crystal lattice.
One noteworthy result is the significant increase in photoresponsivity when a gate voltage is applied. The application of a gate voltage can enhance the photoresponsivity by an order of magnitude, underpinning the importance of the vertical p-n junction in enhancing device performance. This sensitivity to alignment and gate voltage elucidates the potentials of BP-based photodetectors in polarization-sensitive optoelectronic applications.
Theoretical investigations into the electronic band structure, facilitated by ARPES and ab initio calculations, reveal BP's distinct band gap and highly anisotropic effective masses. These calculations justify the experimentally observed linear dichroic properties and contribute to the understanding of BP's anisotropic nature.
Practically, this research indicates promising avenues for developing high-performance optoelectronic devices using BP. The inherent polarization sensitivity, combined with efficient carrier mobility and low effective mass, shows BP's potential as an integral component in next-generation optical and optoelectronic devices. Moreover, the rapid photoresponse observable with these devices suggests their feasibility in ultrafast applications, opening up new possibilities in the integrated photonic circuitry.
Looking ahead, advancements in BP-based devices could involve optimizing the p-n junction configuration to further exploit BP’s unique optical and electronic properties. Furthermore, hybrid structures involving BP could be explored for enhancing the range and sensitivity of photodetection technologies.
In summary, the showcased linear-dichroic broadband photodetector leveraging BP represents a significant step in utilizing anisotropic 2D materials for practical applications, providing a foundation for expanding their use in advanced optoelectronic systems.