Nanoheteroepitaxy: Nanofabrication route to improved epitaxial growth

Nanoheteroepitaxy is a fundamentally new epitaxial approach that utilizes t hree-dimensional stress relief mechanisms available to nanoscale heterostru ctures to eliminate defects provided the island diameter is below a critica l value 2l(c),. Analysis shows that 2l(c)similar to (15-30)X the critical t hickness h(c). In the case of GaAs on Si (similar to4% misfit), 2l(c)simila r to 40nm. In material systems such as GaN on Si (similar to 20% misfit), w here the misfit is much larger and interfacial defects are unavoidable, the nanoheteroepitaxial structure is shown to reduce the formation and propaga tion of threading defects. Nanostructured substrate parameters that impact growth are discussed and interferometric lithography is introduced as a met hod for fabrication of large-area substrates for nanoheteroepitaxy, Si nano island diameters as small as 20 nm are demonstrated. Scanning and transmiss ion electron microscopy data of GaN grown on Si (iiia organometallic vapor phase epitaxy) shows reduced threading defects in nanostructured samples co mpared to growth on planar substrates. Photoluminescence intensity data of nanostructured samples is enhanced by similar to 100X as compared to planar -growth samples. (C) 2000 American Vacuum Society. [S0734-211X(00)11206-5].