On Preparation And Optical Absorbance Properties Of (Si/Ge)_n/SiGe Thin Multi-films

Film solar cells have a lot of characteristics, such as economize on resources, process simple,low cost and high efficiency, and have important application in the field of aerospace, communicationand micro power electronic products. Among all kinds of film solar cells, film solar cell in Simaterials is one of the most important direction. The goal of this paper was to broaden the response ofthe solar spectrum range and improve the photoelectric conversion efficiency. We used （Si/Ge）_nsuperlattice as the research object, making （Si/Ge）_n/quartz thin multi-films by JPG500magnetronsputtering instrument and discussing the relationship among superlattice cycle number, single layerthickness and light absorption properties of μc-（Si/Ge）_n/pc-（Si/Ge）_n/SiGe thin multi-films. Analysedthe crystalline properties, surface and interface images, optical absorption properties and mechanicalproperties of the films by XRD, Raman, SEM, UV-Vis and scratch test method.Cycle number and single layer thickness of the （Si/Ge）_nsuperlattice film had big effect on thecrystallization properties and light absorption properties. The optical band gap gradually decreasedwith the increase of the film cycle number; the optical band gap gradually decreased with theincreased of the thickness of Si and Ge film. The best technological parameter was about Ge:120s, Si:480s, for5layers. At this time, the diffusion of the film between layers was minimum, and thecrystallization rate was the highest（16.4%）, the optical band gap was1.62eV, and the response of thesolar spectrum range was to550nm.The holdingperiod, temperature rate and annealing temperature had effect on the crystal grainsize. The grain diameter increased with the longer of holdingperiod; When the temperature rateincreased from5℃/min to10℃/min, the grain diameter variation amplitude was larger than the rateincreased from10℃/min to20℃/min. With the increased of the annealing temperature, the crystalsize first increased, then changed unobvious, when annealing temperature was at800℃, the graindiameter got to the biggest（14nm）. The best annealing parameters was about800℃,10℃/min,3h. Atthis time, the film was not in the stress state; the combination strength of the film was the largest（7.06N）; the response the solar spectrum range was to635nm, and the optical band gap was1.46eV.SiGe alloy layer could increase the crystallization properties of （Si₈/Ge₂）₅, the crystallizationproperties of （Si₈/Ge₂）₅with SiGe alloy layer was105.5%higher than that of （Si₈/Ge₂）₅; thecombination strength of （Si₈/Ge₂）₅with SiGe alloy layer was8.78N, which was1.5times of（Si₈/Ge₂）₅. After sedimentary microcrystal layer, the combination strength of μc-（Si₈/Ge₂）₅/poly-（Si₈/Ge₂）₅/SiGe/quartz was decreased to6.15N, which was32%lower than that of poly-（Si₈/Ge₂）₅/SiGe/quartz,because the sedimentary microcrystal layer could increase the multi-layer interface; however, theresponse of the solar spectrum range was to680nm, and the light absorption performance wasimproved.