Researchers have made significant strides in the development of deep ultraviolet (DUV) photodetectors, thanks to innovations involving two-dimensional materials. Traditional DUV photodetection systems have struggled with their reliance on wide-bandgap semiconductors, which face challenges such as high dark currents and difficulties in material growth. The new approach focuses on tunneling barrier modulation, effectively enhancing photodetection sensitivity.
The newly developed device uses van der Waals heterostructures, integrating MoS2 as the charge transport layer, few-layered graphene (FLG) as the photon absorption layer, and hexagonal boron nitride (hBN) as the dielectric barrier. This combination has yielded impressive results: the device exhibits record-breaking photoresponsivity of 4.4 × 106 A·W-1 and specific detectivity of 1.4 × 1017 cm·Hz-1/2·W-1 at 250 nm UV light with minimal light intensity.
Remarkably, the DUV photodetector demonstrates exceptional capability, showing a rejection ratio exceeding 106 for visible light, owing to its innovative cutoff wavelength mechanism based on tunneling barrier height rather than material bandgap. This allows the device to be adaptable across different materials, opening the door for wider applications.
For example, the photodetection scheme has been extended to include various charge transport layers such as ReS2 and different dielectric and photon absorption materials. These adaptations have enabled the photodetector to achieve high performances across different wavelengths, with cutoff wavelengths identified at 440 nm and 375 nm corresponding to different operational modes. Consequently, researchers have successfully employed the MoS2/hBN/FLG device as a precise UV power meter, capable of detecting weak UV radiation down to measurements of 0.1 μW·cm-2. Results have matched weather reports from meteorological agencies, confirming the reliability of the device.
Operating under varying environmental conditions has proven effective, with the ability to measure solar UV irradiance, aligning seamlessly with regulatory UV safety standards. The integration of quartz lenses has also allowed for increased sensitivity and quicker response times, achieving significant performance improvements for applications such as environmental monitoring and healthcare.
This innovative photodetection technology marks a substantial advancement, overcoming previous limitations tied to conventional semiconductor materials. The integration of diverse materials, alongside the tunneling barrier modulation concept, opens up possibilities for future optoelectronic applications, presenting commercial advantages and opportunities for various industries.
Overall, the tunneling-barrier-engineered DUV photodetectors have been validated for their significant potential as sensitive DUV photodetectors based on van der Waals heterostructures. This work not only pushes the boundaries of material science but also highlights the researchers’ commitment to developing technologies adaptable for practical use.