Infrared Analysis Of Hydrogenated Amorphous Silicon By Ab Initio

Amorphous has strong photoconduction and large optical absorption coefficient. It can not only change the conductivity type by doping, but also be continuously adjusted its optoelectronic properties through controlling the deposition conditions. a-Si:H had been widely used in military and civil fields as an excellent semiconductor material. Unfortunately, the existence of dangling bonds in the conventional amorphous silicon material would deteriorate the stability of material, affected the performance of amorphous silicon thin film device. In the past, most researches focused on the impact of processing conditions on the structure and properties of hydrogenated amorphous silicon thin films. Researches of computer simulation were less. In this paper, based on experiment, the model of hydrogenated amorphous silicon was established by the first-principles, and compared the simulation result of structure and infrared properties with experiment results.In this paper, a single crystal silicon model of 2x2x2 with 64 Si atoms was established firstly. Then the amorphous structure of silicon was obtained by using the method of liquid cooling to heat the model, and the simulation results showed that this structure goodly reflected the short-range order and long-range disordered nature of amorphous silicon. Further more, the density of the amorphous model impact on its structure and properties had been studied, and found that when the density of the model was 2.20 g / cm3 the model had lower defects and model properties were more stable.Then we conducted some experiments and analysis of experimental film for more in-depth understanding of the importance of the H atoms in the amorphous silicon film and establishing ideal hydrogenated amorphous silicon model. The hydrogen content of these films had made a quantitative calculation. We studied how the hydrogen content of the film changes with pressure, found that hydrogen content of the film with increase as pressure increased firstly and then decreased, the reaction pressure was 80 pa the maximum hydrogen content was reached. The film bonding mode, the refractive index and extinction coefficient of the different hydrogen content models were analyzed. Experimental part could not only deepened the film structure and properties of infrared awareness but also provide an experimental basis for a reasonable simulation model verification.Finally, the amorphous model was added H atoms, established some models of different hydrogen content of the amorphous silicon, we studied the effects of the hydrogen content of the model structure and properties of the model, found 11% hydrogen content model had lower defect density and lesser degree of phase transformation, in which H atoms presented as Si-H in the nature of the model were stable. Then we calculated the infrared characteristics of the model by first-principles simulation. Further more, we verified the validity of the model by compared with the experimental result.