Optical properties of multiple, delta-doped Si:B/Si layers

Reliable fabrication of high-speed, delta-doped transistors and a better understanding of two-dimensional metal-insulator transitions can be achieved using silicon molecular beam epitaxy (MBE). However, this fabrication technique should be performed with care, avoiding dopant segregation on epitaxial Si surfaces and improving the doping efficiency. Here we report comprehensive structural and optical investigations of MBE-grown Si/delta-doped Si:B multilayer structures. Measurements of Auger electron spectroscopy, Raman scattering, optical reflection and photoluminescence are performed. Our results indicate nearly metallic conductivity at room temperature with a metal-insulator phase transition near T ∼100 K. In contrast to recently reported data, no enhancement of the photoluminescence at room temperature is found. Occasionally, a few samples in specific areas exhibit strong photoluminescence at 1.4-1.6 μm attributable to structural defects, most likely due to B segregation.