Ga₂O₃ metal–insulator-semiconductor solar-blind photodiodes with plasmon-enhanced responsivity and suppressed internal photoemission

Abstract

Metal-semiconductor-metal (MSM) architectures are popular in achieving high-responsivity Ga2O3 solar-blind photodetectors (SBPDs), whereas the hot-electron-induced internal photoemission (IPE) effect restricts the detecting performance. Herein, we demonstrate the rational design of an Al/Al2O3/Ga2O3 metal-insulator-semiconductor (MIS) SBPD that has merits of enhanced responsivity, suppressed sub-gap response and ultralow dark current based on the simulation results obtained by using Lumerical software. For the cylindrical patterned detectors with Al/Al2O3/Ga2O3 MIS structures, the optimized dimensions of Al electrodes with a conformed ultra-thin (2 nm) Al2O3 layer well support the surface plasmon polariton (SPP) resonances at 250 nm, thus improving the photoresponsivity to be 74 mA/W. Furthermore, the sandwiched Al2O3 layer lifts up the barrier for hot electrons in electrodes, which significantly suppresses the IPE-induced sub-gap photoresponse by more than 105 in magnitude with respect to the Al/Ga2O3 MSM counterpart. Optical and electrical field distributions are overlapped in cylindrically patterned MIS detectors, simultaneously improving the excitation and collection efficiencies of excess carriers and resulting in the 103-boosted rejection ratio.