Luminescence from erbium implanted silicon-germanium quantum wells

We have investigated the luminescence emitted at 1.54 μm from erbium-implanted strained ultrahigh vacuum chemical vapor deposition-grown (UHVCVD-grown),Si_1-xGe_x quantum wells. Germanium fractions of up to 13% were used, and all well widths were below the critical thickness for pseudomorphic growth. A preliminary study was carried out on Si_1-xGe_x quantum wells implanted wich amorphizing doses of silicon at 77 K in order to study the regrowth across the interfaces, and subsequent structural and optical recovery. After amorphization and regrowth by a two stage anneal process, transmission electron microscopy (TEM) clearly showed the presence of the quantum wells, with sharp contrast. X-ray diffraction (XRD) studies showed that good regrowth has been achieved, with line widths very similar to the original material. However, the photoluminescence (PL) was found to be dependent upon the duration of the first anneal. Increasing the anneal time resulted in PL spectra being dominated by broad signals between 0.9 and 0.97 eV associated with structural defects. High concentrations of erbium were incorporated into the strained Si_1-xGe_x quantum wells by implantation and solid phase epitaxial regrowth. TEM and XRD studies showed that the quantum wells retained their structure, with negligible segregation or diffusion of the germanium during the recrystallization. Erbium-related emission centered at 1.54 μm was observed in the implanted Si_1-xGe_x layers after regrowth, and generally found to be of similar intensity as that in bulk silicon implanted with more than an order of magnitude higher dose of erbium.