Fabrication of Si/SiOィイD22ィエD2-based crystalline heterostructures by using low-energy oxygen implantation during Si molecular beam epitaxy

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A novel technique is developed to create truly "epitaxial" Si/SiOィイD22ィエD2-based heterostructures. The new technique is a variant of Si molecular beam epitaxy which features a low-energy oxygen ion implanter, referred to as hybrid epitaxy. Controlling the kinetics of internal oxidation and disruption of Si encompassed by a wide-gap SiOィイD22ィエD2 matrix in a separation-by-implanted oxygen (SIMOX) geometry allows a rich variety of Si/SiOィイD22ィエD2- and SiGe/SiOィイD22ィエD2-based quantum nanostructures. Fabrication of Si quantum wells, quantum wires using either a V-grooved substrate or cleave-edges of SIMOX, and a stacked array of quantum dots have been successful. What characterizes most such a wide spectrum of quantum structures is the fact that the Si or SiGe features maintain crystalline coherence transmitted from the substrate. As a result, Si and SiGe quantum dots are of highly-oriented nature, i.e., the feature hardly attainable otherwise.In view of conceivable applications, an attempt … More was made to fabricate key components in the field of optoelectronics. For example, creating Bragg mirrors offering a normal incidence reflectance of 90% at designated stop-band wavelengths has enjoyed much success, which in turn has a high potential for use as a virtual substrate for regrowth. In the same context of virtual substrate, SiGe-OI structures recently have become of particular importance to the electronics as they not only comply with the demand for SOI but a high electron mobility transistor can be readily obtained simply by growing a tensilely-strained Si channel atop. Thoroughly studying the energetics and kinetics of the evolution of SiGe-OI, it has been found that a good SiGe-OI is permitted in a narrow window region in tens of the Ge contents and accordingly there is a x-value ceiling (x<0.3) for the starting SiィイD21-xィエD2GeィイD2xィエD2 layers which may or may not have been strain-relaxed. Selective oxidation of Si and concomitant desorption of GeO due to a thermal budget given to the samples during the annealing step of the SIMOX process is responsible for the erosion or total loss of SiGe for x values larger than 0.3. In contrast, by using SiGe alloys with x<0.18, a record value of 8-nm was obtained as the thickness of the top SiGe.An interesting observation made for SiGe-OI is the development of a strong optical absorption band located around 1.2eV. The new band shows up only after oxidation and is originated from the near-surface region which was confirmed as quenching of the bulk photocurrent for a series of MSM Schottky-type photodetectors in a lateral configuration. Less