Deposition Of Ge Film On Monocrystalline Si Substrate With Cut-off Angle

Comparing with the single-junction solar cells,GaInP/GaAs/Ge triple-junction solar cells has the broader absorption spectrum of sunlight which improves photoelectric conversion efficiency of solar cells to 44.4%under concentrated conditions,thus GaInP/GaAs/Ge triple-junction SCs become the focus of solar cells with high-efficiency.Due to the rare resource of Ge material and the large thickness of Ge bottom cell,Ge layer increases the cost of multi-junction solar cells.Growing Ge film on heterogeneous substrate as bottom cell becomes another research direction.Currently,there are four main research technologies that use resource-rich single crystal Si as substrate for Ge film growth:gradient buffer layer,low temperature Ge buffer layer,patterned substrate and monocrystalline Si substrate with cut-off angle.This paper focuses on characteristics of Ge film deposited on the monocrystalline silicon with cut-off angle,then studies the influence of Ge film quality when Ge film deposited on the Si substrate with cut-off angle which has deposited the gradient buffer layer.Ge film was deposited on Si substrates by magnetron sputtering technology,the Si substrates has four kinds,they are Si(100)Si(1 00)misorients(110)6°,Si(100)misorients(110)10°,Si(100)misorients(111)8° monocrystalline Si substrate.The subsequent heat treatment on the sputtered Ge film was carried out to improve the crystal quality of Ge film,the annealing duration and temperature of heat treatment also has important effects on the recrystallization of Ge film.The quality of Ge film were characterized by XRD,SEM,AFM and other characterization techniques,observing the quality of Ge film and analyzing the influence of different preparation technologies on Ge film.After theoretical calculation and experimental analysis,the main results are as follows:(1)In the Ge/Si film structure,Ge films were deposited on Si(100),Si(100)misorients Si(110)6°,Si(100)misorients Si(111)8° and Si(100)misorients Si(110)10°monocrystalline substrates.Ge films deposited on Si(100)misorients Si(111)8° has the best preferred orientation of Ge(111),the ratio of the diffraction intensity between Ge(111)and Ge(220)crystal plane reaches 3.453.(2)In the Ge/Si1-xGex/Si structure,Ge films were deposited on Si(100),Si(100)misorients(110)10° and Si(100)misorients(111)8° monocrystalline Si substrates.The ratio of the diffraction intensity between Ge(111)and Ge(200)crystal plane in Ge film deposited on Si(100)misorients Si(110)10° Si substrate reaches 7.118.(3)In the Ge/Si1-xGex/Si structure,Si1-xGex and Ge films deposited on Si substrates in different substrate temperatures has the preferred orientation of another crystal plane.According to the experimental results,Ge films showed the preferred orientation of Ge(200).I Ge(220)/I Ge(111)is 6.754 in the Ge film which deposited at 450? on Si0.1Ge0.9 buffer layer that was deposited at 300? through 2h conditional thermal annealing.The growth of Ge film is affected by Si1-xGex buffer layer,and the crystal growth direction is from the bottom to top,the preferred orientation of Ge film is changed from Ge(111)to Ge(220).The monocrystalline Si substrate with cut-off angle could promote the growth of Ge film.The cut-off angle changes the atomic arrangement of Si substrate surface during Ge film deposition,and reduces the lattice mismatch between Ge film and Si substrate.The existence of Si1-xGex buffer layer reduces lattice mismatch further,Ge film deposited on heterogeneous substrate have better nucleation and crystallization environment.The influence of Si1-xGex buffer layer on Ge film also relates to the substrate temperature during sputtering process.