Effect of embedding of CrSi2 and β-FeSi2 nanocrystals into n-type conductivity silicon on the transport and thermal generation of carriers

Abstract

The possibility of ordered embedding of CrSi2 and β-FeSi2 nanocrystals (NCs) into a Si(111) substrate of n-type conductivity has been demonstrated. The types of NCs and silicon matching were determined, and the types of the crystal lattice deformations of CrSi2 and β-FeSi2 NCs were established. For six-layer heterostructures with embedded CrSi2 and CrSi2 + β-FeSi2 NCs, a change in the Seebeck coefficient sign from negative to positive was observed for the first time in a 250–400 K temperature range, which indicates a nanocrystals to silicon hole injection. An estimate was made of the minimum number of holes, injected from a single nanocrystal, which are necessary to compensate for the thermo-emf from an n-type substrate. Band diagrams were constructed for the β-FeSi2-p NC/Si-n and CrSi2-p NC/Si-n heterojunctions, and the discontinuities in the valence and conduction bands were determined. The minimum barrier (0.065 eV) for holes in the Si-p/NC β-FeSi2-p/Si-n system indicates their thermal generation as the main mechanism. The main mechanism of hole injection from Si-p/NC CrSi2-p/Si-n system is tunneling through the surface states in the Si band gap due to the large discontinuity (1.075 eV) in the Si valence band.