| In the development of semiconductor materials in recent years,Ⅲ-nitrides plays an important role in it.GaN has been widely used in many fields,and the research upsurge of InN is being set off.InN possess minimum electron effective mass,maximum electron saturation velocity,minimum band gap and the highest electron mobility among Ⅲ-nitrides.This,and other excellent properties make it a kind of promising material in the applications of solar cell,detector,and high-frequency devices.Ⅲ-nitrides semiconductor can form an alloy system with continuously adjustable direct band gap from 0.7 eV(InN)to 6.2 eV(AIN).In the InGaN ternary system,the band gap from 0.7～3.4 eV can be adjusted by proper composition control,so that solar cells covering almost the whole solar spectrum can be prepared.However,due to the low decomposition temperature of InN and other limits,the crystal quality of InN grown by some traditional technologies was not so great.In this thesis,InN and InGaN thin films were grown by PE-ALD.For the growth of InN,I established the ALD window for growth,and explored the growth temperature,and plasma power etc.After optimizing the basic growth parameters,several different substrates(Si,Al2O3,GaN,ZnO)were selected to explore the growth of InN.The results of high resolution XRD show that InN on ZnO single crystal substrate has the best crystal quality.this is obtained under the temperature of 250℃ and the plasma power is 200 W.Phi scanning results showed that the(10-11)peak positions of InN film and ZnO substrate were exactly the same,which indicated that the crystal preferred orientation of InN film and ZnO substrate were exactly the same.this confirmed that InN epitaxy was realized on single crystal ZnO substrate.HR-TEM results showed that the ratio of InN to ZnO lattice sites was 11/12,which was exactly consistent with the lattice mismatch values of InN and ZnO.This result showed that InN was fully relaxed on the ZnO surface at the initial growth stage,which further confirmed the epitaxial growth of InN on the single-crystal ZnO substrate.Based on the establishment of InN ALD growth,the InGaN growth process of PE-ALD was studied.Due to the particularity of ternary materials,two growth formulations were designed.One method could be called digital scheme which is to alternate the growth of InN and GaN atomic layers,and regulate the components by controlling the periodic ratio of InN and GaN layers.In the other method(mixed source scheme),three kinds of sources are fed successively,and the components are regulated by regulating the pulse time of TMI and TEG.The results of this work show that the mixed source scheme is easier to control the In component of InGaN films.Finally,prototypical InGaN-based solar cells was prepared. |
