Unveiling the synergic potential of dual junction MoSe2/n-Ga2O3/p-GaN heterojunctions for ultra-broadband photodetection†

Abstract

For practical optoelectronic applications, photodetectors capable of detecting light across a wide wavelength range (200–1100 nm) are essential. Heterojunction semiconductors play a crucial role in developing such multi-wavelength photodetectors. In particular, the heterojunction of transition metal chalcogenides (tuneable bandgap and high electron mobility) and Ga₂O₃ (wide bandgap of >4 eV) is a significant research topic for photodetector fabrication exhibiting an ultrawide spectral photodetection capability. In this study, epitaxial β-Ga₂O₃ thin films were grown on atomically flat sapphire (0001) and p-GaN/sapphire (0001) surfaces using a pulsed laser deposition technique. The effect of the substrate on the crystalline, optical, electronic, and photoresponse properties of β-Ga₂O₃ thin films was thoroughly investigated and correlated with theoretical insights from density functional theory. To achieve broadband photodetection, a heterojunction of MoSe₂ and the as-grown Ga₂O₃ films was fabricated, enabling light detection from the deep ultraviolet (UV) to the near-infrared (NIR) spectral regions. The MoSe₂/Ga₂O₃/p-GaN device exhibited an expanded detection range from deep ultraviolet (240–320 nm) to long-wavelength ultraviolet (320–400 nm) and a significant responsivity of 5.5 A W⁻¹ in the NIR region, nearly fourfold higher than that of the MoSe₂/Ga₂O₃/sapphire device. These results highlight the potential of these hybrid structures for developing multi-wavelength photodetectors with high photoresponse across the deep-UV to NIR spectral regions, offering promising applications in fields ranging from environmental monitoring to communications.