Studies of light emission and epitaxial growth on crystal surfaces

The integration of novel structures and devices into semiconductor electronics requires a detailed understanding of the physical phenomena exhibited by impurities at crystal surfaces. Using this understanding, the optical properties and structure of deposited atoms can be selected. This thesis describes studies of light emission from a fraction of a monolayer of Er atoms on a silicon surface and of the low-temperature growth and doping of crystalline Si thin films mediated by Pb.;Erbium atoms at an As-terminated Si (111) surface can be made to emit light at the 1.55 gin wavelength associated with an internal transition in the Er3+ ion. The As-terminated surface suppresses competing non-radiative surface recombination mechanisms. Following the deposition of Er, its characteristic light emission is observed only after oxygen reacts with the surface. The intensity of the light emitted by Er increases significantly upon cooling. No light emission was observed from Er atoms deposited on 7 x 7 or H-terminated surfaces.;A monolayer of Pb mediates high-quality homoepitaxial growth on Si (111) surfaces at temperatures where growth with other overlayer elements or on bare surfaces leads to amorphous or highly defective crystalline films. Nearly defect-free epitaxy proceeds at temperatures as low as 310°C for film thicknesses up to 1000 A with no sign that this is an upper limit. When Pb and Si are deposited on an As-terminated Si (111) substrate, the Pb floats on the surface of the growing Si film and the As layer remains buried at the substrate-film interface. Because the Pb overlayer mediates growth without doping the film, the electrical properties are determined by the As atoms. With a donor density in excess of 1 x 1021 cm --3 in a layer less than 50 A in thickness, the heavily doped interface region represents the highest concentration of electrically active As achieved by any delta-doping method.