Rapid Synthesis Of Si Nanocrystal Embedded In SiC Matrix Produced By Hot Wire CVD At Low Temperature

Silicon-based tandem solar cells has attracted more attentions as one of the third generation solar sell concepts due to its compatible with the Si technology. The most important part in silicon-based tandem solar cell is the film of Si nanocrystal embedded in Si-based matrix. Si-based matrix involve the SiO2, Si3N4, and SiC, in which the SiC can provide the lowest barrier for Si nanocrystal, and so lead to high current. Nowadays, Si-QD:SiC are deposited widely by low-temperature CVD with sequential high-temperature annealing, which is complex and involves the high-temperature process. This report investigated the possibility of low-temperature deposition of Si-NC:SiC film by how-wire CVD.The concept, principles, development status and the existent problems for Si-based tandem solar cells were introduced firstly, and then the features of hot-wire CVD were analyzed and compared. The Si-NC:SiC films were deposited by HWCVD with mixture gases of SiFH4+CH4+H2in a low substrate temperature at250℃and300℃. The film properties were characterized by Raman. XRD. SEM, FTIR, transmission spectrum and Hall effect. The results clearly show that:(a)The deposited films have the Si-NC:SiC structure with a mean size of ten nm.(2) When TF=1900℃, Ts=300℃, the increasing of R from5%to25%leads to reducing of the growth rate from21.3nm/min to13.6nm/min, increasing of the optical bandgap from2.01eV to2.19eV, decreasing of the size of Si nanocrystal from16nm to8nm and decreasing of the crystal volume fraction from29.1%to8.5%. The experimental results are explained in terms of the growth model of Si nanocrystal and the effect of hydrogen dilution.(3) When TF was kept at a constant, the increasing of Ts lead to increasing the growth rate and decreasing the optical band gap. Moreover, an increasing of TF leads to an increase of both the growth rate and optical band gap when Ts unchanged.(4) The increasing of B2H6doping ratio increase from3%to3.8%leads to a decreasing of the dark resistivity and a increasing of the carrier concentration. This can be explained by using the doping mechanism of B2H6...