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Microcrystalline silicon germanium film as a narrow band gap material , has the advantages of high absorption coefficient , tunable band gap is very promising tandem solar cells bottom cell absorber material . But the film of germanium increases , the increased defect states , impact and optical properties of the thin film , and impede its practical application in the solar cell . In this paper, the Si 2 H 6 and GEH 4 < / sub > and the SiH 4 < / sub > and GeH 4 combination of two gases as a source gas , a VHF plasma enhanced chemical vapor deposition ( VHF - PECVD ) the preparation of the silicon-germanium film , Research germanium impact on the film properties . SiH 4 and the GEH 4 < / sub > film series prepared compared the Si 2 < / sub > H 6 and GEH 4 < / sub > prepared thin film of germanium into the rate is relatively slow ; the Si 2 < / sub > H 6 < / sub the > and GEH 4 < / sub > prepared silicon germanium With the increase of the concentration of germanium alkoxy thin film structure , the film always to keep a certain degree of ordering . The GeH 4 and Si 2 H 6 films grown under the premise to keep a certain proportion of crystallization , photosensitivity relatively high . Compared with SiH 4 , Si 2 H 6 in microcrystalline silicon germanium films grown with the GEH 4 < / sub > combination certain advantages. Using the the Si 2 < / sub > H 6 < / Sub > and the GEH 4 < / sub > as the source gas preparation of microcrystalline silicon germanium film by adjusting the temperature of the substrate during the reaction , the total gas flow , plasma power and pressure , and other parameters , to optimize the microcrystalline silicon germanium film . Eventually found : As the substrate temperature increases , the increase in film orderly degrees ; With the increase of the total gas flow , the film growth rate is increased , the crystallization rate is gradually reduced ; With the increase in power increases the crystallization rate of the material , but when power exceeds a certain value , positive ion bombardment of the surface of the film is enhanced , increasing the probability of defects generated and cause deterioration of the photoelectric characteristics of Assembly ; reaction pressure caused by the film tends to be amorphous , the reaction pressure is too small , easily causing defect states increase , reducing the quality of the film . Eventually, the substrate temperature as 190 ° C , alkoxy germanium concentration of 10% , glow lamp power 12W pressure of 100Pa conditions , the prepared crystallization rate of 42.7% , a Ge content of 20% , photosensitivity of the order of magnitude of 103 microcrystalline silicon germanium film .
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