Realization of dislocation-free epitaxy using nanochannel epitaxy

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In highly mismatched heteroepitaxy, dislocation-free layer can be grown in case the layer is laterally grown from an extremely narrow line opening cut in a selective growth mask. It is because the residual stress should be reduced below the threshold for the generation of dislocations with the help of the 3-dimentional structure shaped by the narrow opening. The new method of lateral growth with the extremely narrow channel was named as "nanochannel epitaxy (NCE)" and set as the main target of this research project.The following items should be addressed to fabricate a narrow opening with nanometer size and to perform NCE :1)Development of nano-lithographic technique using scanning tunnel microscopy (STM),2)Development of lateral growth technique performed by molecular beam epitaxy (MBE).The following themes were also studied in the research project,3)Droplet epitaxy of nano structures, e.g.quantum dots,4)Fabrication of vertical-cavity surface-emitting laser (VCSEL) using molecular bea … More m epitaxy in situ reflectance monitor.Consequently, the following results were obtained :1)STM lithography was realized on an oxide on (001)GaAs substrates, on an native and thermal oxides on (111)Si substrates. The lithography conditions were optimized and the mechanism for nano-lithography were studied.2)Beam induced lateral epitaxy (BILE), which enables a lateral growth using MBE, was studied. BILE of GaAs layer was performed on (111)GaAs substrates. BILE was also applied on the lateral growth of GaAs layer on (111)Si substrates and, consequently, dislocation-free areas of GaAs were successfully grown on the substrates.3)Importance of GaN-related materials and the fine matching between droplet epitaxy and NCE led us to the study on droplet epitaxy of GaN dots. As a result, high density (10^<11> cm^<-2>) and small sized (10nm in diameter) GaN dots were successfully fabricated and the effect of annealing on the degree of the nitridation was also ascertained.4)A VCSEL was fabricated using an in situ reflectance monitor by MBE. Both the center wavelength of the stop band of the distributed Bragg reflector (DBR) and the resonant wavelength of the optical cavity were successfully controlled using the monitor. The desirable laser performance of the VCSEL fabricated from the wafer indicates marked increases in the controllability and reproducibility of growth with the aid of the in situ reflectance monitor. Less