Hexagonal boron nitride (hBN) has emerged as a promising material for ultraviolet (UV) photodetection due to its intrinsic wide bandgap, which enables deep-UV sensitivity without the need for external filtering. With a bandgap of approximately 6 eV, hBN exhibits strong absorption in the UV-C range (200–280 nm), making it suitable for applications such as flame detection, environmental monitoring, and secure communications. Unlike conventional UV materials like silicon carbide (SiC), hBN demonstrates superior solar-blind characteristics, meaning it remains insensitive to visible and infrared radiation, reducing false signals in high-background environments.

Device architectures for hBN-based UV photodetectors primarily include phototransistors and photodiodes, each offering distinct advantages. Phototransistors leverage the high carrier mobility and gain mechanisms in hBN to achieve high responsivity. For instance, back-gated hBN phototransistors have demonstrated responsivities exceeding 1000 A/W under deep-UV illumination, attributed to photoconductive gain. This gain arises from prolonged carrier lifetimes due to trap states within the hBN lattice or at interface regions. However, this mechanism also introduces trade-offs in response speed, with some devices exhibiting slow recovery times on the order of seconds.

In contrast, hBN-based photodiodes prioritize speed over gain, with reported response times in the nanosecond range. These devices often employ metal-semiconductor-metal (MSM) or p-i-n configurations. MSM photodiodes, for example, utilize interdigitated electrodes on hBN flakes to achieve low dark currents, typically in the picoampere range, while maintaining reasonable responsivity (1–10 mA/W). The absence of dopants in pristine hBN complicates p-i-n diode fabrication, necessitating innovative approaches such as van der Waals heterostructures with other 2D materials to create built-in electric fields for efficient carrier separation.

Noise performance is a critical metric for UV photodetectors, particularly in low-light conditions. hBN devices exhibit low noise equivalent power (NEP), often below 1 pW/Hz^(1/2), owing to the material’s high resistivity and low defect density when synthesized under optimal conditions. However, inconsistencies in material quality across different growth methods can lead to variable noise characteristics. For instance, chemical vapor deposition (CVD)-grown hBN may contain more impurities than mechanically exfoliated flakes, increasing generation-recombination noise. Careful device passivation and contact engineering are essential to mitigate these effects.

Compared to conventional UV materials like SiC, hBN offers several advantages. SiC, with a bandgap of ~3.3 eV, requires additional optical filters to achieve solar-blind operation, adding complexity and cost to the detector system. In contrast, hBN’s larger bandgap inherently blocks longer wavelengths, simplifying device design. Additionally, hBN’s layered nature allows for ultra-thin, flexible detectors, whereas SiC devices are rigid and bulkier. However, SiC still outperforms hBN in terms of technological maturity, with well-established doping techniques and commercial availability of high-quality substrates.

Scalability remains a significant challenge for hBN UV photodetectors. While small-area devices fabricated from exfoliated flakes show excellent performance, wafer-scale production is hindered by non-uniformities in CVD-grown hBN films. Defects such as grain boundaries and incomplete crystallinity can degrade responsivity and increase dark current. Advances in epitaxial growth, such as the use of single-crystal substrates for hBN deposition, are being explored to address these issues. Another bottleneck is the lack of reliable p-type doping methods for hBN, limiting the design flexibility of homojunction devices.

Environmental stability is another consideration. Although hBN is chemically inert and resistant to oxidation, prolonged exposure to high-energy UV radiation can induce defect formation over time, gradually degrading detector performance. Encapsulation strategies, such as sandwiching hBN between other stable 2D materials, have shown promise in enhancing operational lifetimes.

In summary, hBN-based UV photodetectors excel in deep-UV sensitivity and solar-blind operation, outperforming traditional materials like SiC in specific metrics. Phototransistors and photodiodes each offer unique benefits, with trade-offs between responsivity and speed. Noise performance is generally favorable but sensitive to material quality. Scalability challenges, particularly in growth uniformity and doping, must be overcome to enable widespread adoption. Continued research into large-area synthesis and device integration will be crucial for advancing hBN UV photodetectors toward practical applications.