The key issues for growing III-V compound layers, free of structural defects, on Si substrates are clarified. The technologies for overcoming the fundamental problems have been developed. As a result, it has been clarified that dislocation-free III-V-N alloys can be grown on Si substrates whose lattice constants are matched to those of Si. Device structures of the GaAsPN/GaPN quantum well structure and the Si/GaPN/Si structure have been successfully grown on a Si (100) substrate covered with a thin GaP initial layer. The grown layers and hetero-interfaces contained no threading dislocations and no misfit dislocations, respectively. Neither stacking faults nor anti-phase domains were observed. A key issue for application to novel devices is the increase in nitrogen composition without degrading optical and electrical properties.
Anisotropic step bunching on vicinal 6H–SiC(0001) surface induced by H2 etching was investigated. Step structures were observed using atomic force microscopy and high-resolution transmission electron microscopy at off angle <2°. The etched surfaces exhibited three types of step bunching: (1) straight six-bilayer steps, (2) straight six-bilayer steps and nanofacets, and (3) zigzag three-bilayer steps. The step height and density can be controlled by a tilt angle and direction of a vicinal surface. Mechanisms of the step bunching processes are discussed at points of an anisotropy of lateral-etching rates and surface-free energies.
We proposed a Si/III–V–N compound semiconductors/Si structure, which is applicable to optoelectronic integrated circuits (OEICs). The feature of this structure is that optoelectronic devices and Si electronic devices could be fabricated by low-temperature planar process at the same time. A dislocation-free and lattice-matched Si/GaP1−xNx/Si (x=2.9%) structure, which is a basic structure for OEICs, was grown by molecular-beam epitaxy. The images of transmission electron microscopy revealed that there were no threading dislocations and misfit dislocations in the epitaxial layers. It was clarified that the Si and GaP1−xNx layers were lattice-matched to Si and had structural high crystalline quality comparable to Si substrates.
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