Intrinsic carrier multiplication in layered Bi_(2)O_(2)Se avalanche photodiodes with gain bandwidth product exceeding 1 GHz

Emerging layered semiconductors present multiple advantages for optoelectronic technologies including high carrier mobilities,strong light-matter interactions,and tunable optical absorption and emission.Here,metal-semiconductor-metal avalanche photodiodes(APDs)are fabricated from Bi2O2Se crystals,which consist of electrostatically bound[Bi2O2]2+and[Se]2−layers.The resulting APDs possess an intrinsic carrier multiplication factor up to 400 at 7 K with a responsivity gain exceeding 3,000 A/W and bandwidth of~400 kHz at a visible wavelength of 515.6 nm,ultimately resulting in a gain bandwidth product exceeding 1 GHz.Due to exceptionally low dark currents,Bi2O2Se APDs also yield high detectivities up to 4.6×1014 Jones.A systematic analysis of the photocurrent temperature and bias dependence reveals that the carrier multiplication process in Bi2O2Se APDs is consistent with a reverse biased Schottky diode model with a barrier height of~44 meV,in contrast to the charge trapping extrinsic gain mechanism that dominates most layered semiconductor phototransistors.In this manner,layered Bi2O2Se APDs provide a unique platform that can be exploited in a diverse range of high-performance photodetector applications.