Abstract
We theoretically study the band structure and photoelectric properties of few-layered black phosphorus based on recent experimental findings [G. W. Zhang et al., Nat. Commun. 8, 14071 (2017)]. According to the experimental findings, it was shown that absorption peaks associated with optical transitions have been observed. For theoretical study, we apply the low-energy k·p method to study the band structure of multi-layer black phosphorus. The optical conductivities σx(ω) and σy(ω) are calculated when the polarized radiation field is applied along the x (armchair)- and y (zigzag)-directions, respectively. Contributions to optical transition from different subbands are considered in the optical conductivity spectrum. Calculation results show that with an increase in the layer number of multi-layer black phosphorus, the band gap becomes small and the subbands evolve into quasi-continuous bands at last. The optical conductivities vary sensitively with changing thickness, doping level, and light polarization.
Highlights
Black phosphorus (BP) is a new two-dimensional direct band gap semiconductor,1,2 possessing many interesting physical properties such as thickness-tunable band-gap,3 anisotropic and fairly high hole mobilities4–7 of about 105 cm2/V s, anisotropic surface plasmons,8,9 and optical conductivities.10 Multilayer BP are bonded layer by layer via the van der Waals force
We have presented a theoretical model for studying the photoelectric properties in ultrathin BP films
The theoretical model proposed here can include the different polarizations of the radiation field and doping levels
Summary
Black phosphorus (BP) is a new two-dimensional direct band gap semiconductor, possessing many interesting physical properties such as thickness-tunable band-gap, anisotropic and fairly high hole mobilities of about 105 cm2/V s, anisotropic surface plasmons, and optical conductivities. Multilayer BP are bonded layer by layer via the van der Waals force. The band gap of BP can vary from 0.3 eV for the bulk material to 2.0 eV for the monolayer.. The band gap of BP can vary from 0.3 eV for the bulk material to 2.0 eV for the monolayer.3 This energy range covers the wavelength from visible to mid-infrared. The tunable band structure and physical properties of few-layered BP and multilayer BP systems make BP an appealing candidate for a wide range of applications in visible and mid-infrared optoelectronic devices, modulators, and sensors. We intend to study the anisotropic optical conductivities in the visible to mid-infrared regime of black phosphorus films. Transition channels are opened, and the optical bandgap can vary in the multilayer BP system. The optical conductivities are obtained by related optical formulas by varying the doping level and thickness
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