Surface Plasmon-Enhanced $\beta-\text{Ga}_{2}\mathrm{O}_{3}$-Based MISIM Solar-Blind Photodetectors

<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}_{2}\mathrm{O}_{3}$</tex> is one of the best materials for solar-blind ultraviolet photodetectors because of its suitable band gap (~4.9 eV) and high breakdown field strength (8 MV/cm). However, photodetectors based on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}_{2}\mathrm{O}_{3}$</tex> still suffer from the problem of relatively low light absorption efficiency. In order to improve the absorption efficiency, a new metal-insulator-semiconductor-insulator-metal (MISIM) type photodetector is proposed here, which is composed of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}_{2}\mathrm{O}_{3}$</tex> film, a passivation layer of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Al}_{2}\mathrm{O}_{3}$</tex>, and an outer metal layer of metal nanoparticles (NPs). The metal which shows strong surface plasmon resonance (SPR) coupling effect with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}_{2}\mathrm{O}_{3}$</tex> films is chosen according to the dispersion relations. Calculation results show that Al NPs is the best choice. Furthermore, the impact of various sizes of Al NPs on the performance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}_{2}\mathrm{O}_{3}$</tex> based photodetectors is systematically studied using the finite difference time domain (FDTD). Simulation results show that Al NPs with a radius of 50 nm can significantly enhance the absorption efficiency of the MISIM-type photodetector within the wavelength range of 200 nm to 300 nm, with the absorption efficiency increasing from 0.1 to 0.3. Notably, the absorption efficiency increased even by 85% at the wavelength of 254 nm. These findings pave the way of fabricating high performance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}_{2}\mathrm{O}_{3}$</tex> photodetectors by decorating metal nanostructures based on localized surface plasmon resonance (LSPR) effects.