The Influence of Structural Defects in Silicon on the Formation of Photosensitive Mn₄Si₇–Si❬Mn❭–Mn₄Si₇ and Mn₄Si₇–Si❬Mn❭–M Heterostructures

The effect of the amorphous transition layer at the interface between Mn₄Si₇ and silicon doped with manganese on the photoelectric properties of heterostructures is considered. It is found that the precipitated Mn atoms on the silicon surface are grouped at high temperatures, forming drops of liquid manganese, which dissolve the near-surface layer of silicon, forming a liquid solution-melt of Mn with Si. As the solution solidifies, Mn₄Si₇ forms, and the Si–Si bonds under the silicide break due to intense diffusion of Si atoms; an elastically deformed Si region forms, which predetermines the evolution of the formation of photoelectric phenomena in the Mn₄Si₇–Si❬Mn❭–Mn₄Si₇ and Mn₄Si₇–Si❬Mn❭–M heterostructures. The microstructure and chemical composition of doped Si❬Mn❭ samples were studied by means of scanning electron microscopy and X-ray energy dispersive spectrometry using a Quanta 200-3D microscope, and the interface structure of the higher manganese silicide (HMS) and Si❬Mn❭ layer at the nanoscale was refined using the Fourier transform of local zones of high-resolution electron-microscopic images. It is concluded that in the process of diffusion doping of silicon with manganese, broken layers on the surface of the crystal deepen the embedding of manganese atoms, facilitate adsorption, dissolution, and diffusion of Mn in the volume of Si, and also enable the formation of an amorphous layer at the interface of higher manganese silicide and the Si❬Mn❭ layer. The presence of an amorphous transition layer facilitates the process of impact ionization of current carriers upon application of external voltage, as well as the formation of photoelectric phenomena: infrared quenching, temperature quenching, high photosensitivity, and long-term relaxation of residual conductivity.