P-μc-Si1?xGex:H thin film by VHF-PECVD

Abstract:

In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium (p-μc-Si_1−xGe_x:H) was deposited by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH₄ and GeF₄ mixtures. The effect of GeF₄ concentration on films’ composition, structure and electrical properties was studied. The results show that with the increase of GeF₄ concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si_1−xGe_x:H material with high conductivity, low activation energy (σ=1.68 S/cm, E _g= 0.047 eV), high crystalline volume fraction (60%) and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail. This work has been supported by National Basic Research Program of China (“973” Project, No.2006CB202602, 2006CB202603), the National Natural Science Foundation of China (No. 60437030), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry.