Abstract
Silicon is the most popular material used in electronic devices. However, its poor optical properties owing to its indirect band gap nature limit its usage in optoelectronic devices. Here we present the discovery of super-stable pure-silicon superlattice structures that can serve as promising materials for solar cell applications and can lead to the realization of pure Si-based optoelectronic devices. The structures are almost identical to that of bulk Si except that defective layers are intercalated in the diamond lattice. The superlattices exhibit dipole-allowed direct band gaps as well as indirect band gaps, providing ideal conditions for the investigation of a direct-to-indirect band gap transition. The fact that almost all structural portions of the superlattices originate from bulk Si warrants their stability and good lattice matching with bulk Si. Through first-principles molecular dynamics simulations, we confirmed their thermal stability and propose a possible method to synthesize the defective layer through wafer bonding.
Highlights
Silicon is the most popular material used in electronic devices
The fact that almost all structural portions of the superlattices originate from bulk Si warrants their stability and good lattice matching with bulk Si
We examined the possibility of creating a defective layer containing Seiwatz chains (SCs), which can lead to the eventual realization of our superlattice structures
Summary
Γth epoBionhtrwraedreiucsa.lTchuelasteevdatluoebsear0e.1h7ig3h, 0er.1t4h1a,na0n.d030a.00−425, oab0−ta2iinnedatformomictuhneidtsipfoolren-a =llo 3w–e5d, direct band gap of a specially designed Si/Ge superstructure[11], indicating that the optical transition was greatly enhanced in our case Such strong dipole-allowed transitions are partly attributed to the large overlap of the band edge states at the interface layers (Figs 2b and 6). Because of the distorted tetrahedral bonds around the interface Si atoms, the p orbital character is significantly enhanced for the CBM state (Supplementary Fig. 2), as in the dipole-allowed transition at the direct gap of c-Si. The calculated absorption coefficients of our superlattices are comparable to those of direct band gap semiconductors, such as GaAs, CdTe, and CuInS2 (Fig. 7a), which are known as good photovoltaic materials. The wafer bonding between the clean and divalent-adsorbed Si(111) surfaces can serve as a promising technique for the synthesis of superlattices containing the defective layers
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