Experimental And Calculating Study Of Surface Bond On Silicon Quantum Face

Silicon is main material of microelectronic devices. But due to the nature of indirect band gap, its luminous efficiency and intensity is not high, so that to achieve silicon-based optoelectronic integration is limited. Since Canham discover bright PL from porous silicon at room temperature in 1990, the silicon-based luminescent materials has attracted widely attention and deeply research. Luminescent properties of the material are mainly determined by its electronic structure. In order to improve the luminous efficiency, we can change the band gap characteristics of the material by impurity engineering and energy band engineering. There are two main ways to achieve the goal:the one is to use quantum confinement effect, the other is the introduction of surface-emitting center.Si-Yb multilayer film structure was prepared on a silicon substrate in different atmosphere with PLD method. Clear threshold behavior was found on EL of sample prepared in nitrogen atmosphere. And EL enhanced with the increase of the layer number. All of those provide a new method for the preparation of LED and quantum cascade lasers on silicon.When the nano-silicon film is fabricated in different atmosphere, surface state is introduced in the form of surface bond. We regard nano-silicon film as an ideal two-dimensional silicon quantum face structure, and it has one-dimensional quantum confinement. The model is built by Materials Studio software. We calculate and analyze the effect of surface band on the electronic structure of silicon quantum face via first-principles based on the density functional theory. We find that the thickness of quantum face, the density of surface bonding atoms and the symmetry of the supercell play a decisive role in band gap. Thus we prove the quantum confinement effect and the band gap narrowing effect, get symmetry effect and curved surface effect, and speculate that the band gap has nothing to do with surface orientation. The band gap become narrow because surface states produce surface level in band gap. All of these can provide reference for energy band engineering and nano-silicon film luminescent enhancement in theory.Almost all of the simulation results of the quantum face show quaSi-direct band gap characteristics, which can effectively improve the radiative recombination efficiency of silicon material. Si-Er bond on surface generate localized energy level in band gap, which can form an effective luminescence center and improve the luminous efficiency of silicon material. These are effective ways to develop silicon-based LED and LD materials and devices.