Er/O doped Si1−xGex alloy layers grown by MBE

Silicon-based light emitting diodes (LEDs) containing an Er/O-doped Si1-xGex active layer have been studied. The structures were grown by molecular beam epitaxy (MBE), with Er and O concentrations of 5 × 1019 and 1 × 1020 cm-3, respectively, using Er and silicon monoxide sources. The microstructure has been studied by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy, and it is found that Er/O-doped Si0.92Ge0.08 layers of high crystalline quality, can be obtained. Electroluminescence (EL) measurements have been performed on reverse-biased Er/O doped diodes both from the surface and from the edge and the emission at 1.54 µm associated with the Er3+ ions has been studied at 300 K and lower temperatures. To evaluate the possibility to use a Si1-xGex layer for waveguiding in Si-based optoelectronics, studies of the refractive index n of strained Si1-xGex as a function of the Ge concentration have been done by spectroscopic ellipsometry in the range 0.3-1.7 µm. At 1.54 µm the refractive index increases monotonically with the Ge concentration up to n = 3.542 for a Ge concentration of 21.3%. © 2001 Elsevier Science B.V.