Study on thin-film growth and solar-cell application on InN

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The purpose of this study is to grow high-quality InN films on Si substrates, and on the basis of that, to clarify the possibility of the fabrication of InN/Si tandem solar cell. Results obtained through the study are summarized as follows ;(1) MOCVD growth of InN directly on Si substrateGrowth of InN directly on Si by using MOCVD method with TMI and NH_3 is unsuccessful because of the formation of amorphous-phase SiN_X on the Si substrate.(2) Nitridation of GaAs surfaces and MOCVD growth of InN on the nitrided GaAs surfacesA GaN layr is formed on GaAs (111) B substrates when the substrate is annealed at 600-900ﾟC in the flowing NH_3. The structure of GaN layr is zincblende-type for the nitridation temperature lower than 700ﾟC and wurtzite-type for the nitridation temperature higher than 800ﾟC.A wurtzite InN layr is epitaxially grown on the wurtzite GaN layr, while on the zincblende GaN layr a zincblende InN is grown only at the initial stage of the growth and the growth of wurtzite InN becomes dominant as the thickness increases. A zincblende GaN layr is formed on GaAs (100) substrates after the nitridation at 600-1000ﾟC.An InN layr grown on GaAs (100) substrates covered with a zincblende GaN layr is composed of both zincblende and wurtzite phases.(3) Heteroepitaxial growth of InN on Si (111) substrates using a nitrided GaAs buffer layrBy using a nitrided GaAs (111) layr grown on Si (111) substrate as a buffer layr, two types of heterostructure, InN/GaN/Si (111) and InN/GaN/GaAs/Si (111), are obtained. The former can be used for InN/Si two-junction tandem solar cell and the latter for InN/GaAs/Si three-junction tandem solar cell.