Low Temperature Growth Of InN Thin Films By Plasma Enhanced Atomic Layer Deposition

Indium nitride(InN),as an important part of group-? nitride semiconductor material system,it has the lowest electron effective mass,the highest carrier mobility and saturation velocity etc..These excellent properties of InN make it widely used in high efficiency and low cost solar cells,sensors,THz radiation etc..Its band gap is about 0.7eV.This is a narrow direct band gap,which makes it possible to adjust the composition of the group-? nitride alloys to extend their spectral range from the infrared to the deep UV.In recent years,there are more and more researches about how to grow high quality InN thin films.The main work is to study the growth of InN and the choice of substrate materials.At present,the most common methods for preparing InN thin film are Molecular beam epitaxy(MBE),metal organic chemical vapor deposition(MOCVD),magnetron sputtering,atomic layer deposition(ALD)etc..Atomic layer deposition(ALD)is a method of self-limiting growth by alternately saturating the surface through introducing a precursor on the substrate.This method has advantages of well film uniformity,low growth temperature,precise control of film thickness,well step coverage an so on.The plasma of the PE-ALD technique,which provide the required growth of N source to further reduce the temperature of the growth process of the InN thin film.In this paper,we use the PE-ALD equipment to study the growth of InN film by ALD mode and the feasibility of Zinc Oxide(ZnO)as a substrate for InN growth was investigated.First,several importment parameters of InN film growth,which are the temperature of source In,the power of RF plasma and the temperature of the substrate,had been studied by several groups of experimental.The samples were charaterized by ellipsometry and XRD,we obtained the paramater optimization of InN growth,and find the temperature window of ALD growth model.Then,using the optimized parameters to prepare InN films simultaneously in Si,GaN,sapphire and ZnO,respectively.Final,we prepared the InN films on ZnO at different substrate temperature,which was to study the influence of the quality by the substrate temperature.Through the contrast of the analysis by XRD(GIXRD and HRXRD),we found that four kinds of substrate on growth of InN film is obtained,but only in the GaN and ZnO substrate showde a strong diffraction at(002)preferred growth direction.The diffraction peak of ZnO is stronger than GaN.(002)is the preferred growty direction of C axis by the growth of InN single crystal.Through the SEM scanning pattern,we found that all the four kinds of substrates were polycrystalline,and the preferred orientation of the ZnO substrate was strong.The SEM pictures show a mosaic structure polycrytalline.The AFM scans showed that the ZnO had a minimum RMS routhness in the range of 2?m×2?m.Finally,the following conclusions are obtained through experimental results:1.the growth rate change with substrate temperature and we found a window of ALD model.At this temperature window,the growth rate is not affected;2.The lattice mismatch of ZnO and InN is similar,and the PE-ALD has solved the drawbacks of Zn O when the ZnO as the substrate.So,ZnO can be used as a substrate of InN film,and it is worth to study.