Erbium-doped Si1-xGex/Si structures for light emitting diodes
LEDs have been fabricated from erbium-doped Si and Si1-x Gex quantum wells, and exhibit radiation at 1.54 µm when operated in forward bias. The strained Si1-x Gex /Si quantum wells were doped with erbium, either by implantation or during MBE growth, for two germanium fractions, 13% and 25% respectively, and their quality was monitored by transmission electron microscopy. PL measurements as a function of temperature exhibit a dependence of the high temperature signal quenching on the germanium fraction. The forward-bias EL and PL from the Er:Si1-x Gex , exhibit different emission energies irrespective of whether the samples are ion implanted or doped during MBE growth. The energy changes are attributed to confinement of injected holes in the electroluminescence measurement by the quantum wells, and subsequent excitation of a different set of Er atoms which may be in the Si1-x Gex host. Electric field effects have been eliminated by performing the EL and PL under identical conditions. This is very encouraging for the potential use of SiGe waveguides in future injection-type silicon-based LEDs.