Deposition of new microcrystalline materials, μc-SiC, μc-GeC by HWCVD and solar cell applications

This paper describes at first the present status of solar cell efficiencies prepared by Hot Wire CVD (HW-CVD), and then preparation techniques of μc-3C(cubic)-SiC developed for innovative solar cell applications by using HW-CVD method are presented. For preparing μc-3C-SiC, monomethylsilane (MMS) and hydrogen were used for reactant gases. The high conductivity of 5 S/cm could be achieved for N doped n-type μc-3C-SiC. For p-type, as-grown Al-doped μc-3C-SiC films showed a relatively high resistivity, but on thermal annealing, the conductivity increased to the level of 1 × 10− 2 S/cm. Monomethylgermane (MMG) and H2 were used to prepare μc-GeC thin films. μc-GeC thin films with a carbon composition of about 7–8% showed a clear shift of absorption coefficient spectra by 0.44 eV, when compared to crystalline Ge. The pin solar cell structures in which all p,i,n layers consist of μc-SiC have been prepared for the first time. It was found that μc-3C-SiC and μc-GeC are the promising candidates as the next generation thin-film solar cell materials, but at present, the film quality is strictly limited by the residual impurity concentration of filament material Re.