We have fabricated high-density Si quantum dots (QDs) with Ge core on SiO 2 by controlling the thermal decomposition of pure SiH 4 and GeH 4 alternately for the selective growth of a Ge core and a Si cap on pre-grown Si-QDs, and studied the effect of H 2 dilution of SiH 4 for Si cap formation on their photoluminescence (PL) properties. PL from the Si-QDs with Ge core observed at room temperature in an energy region from 0.68 to 0.85 eV irrespective of H 2 concentration for the Si cap formation. However, with increasing the H 2 concentration, the intensity of PL originating from radiative recombination between the first-third quantized states in the Si-QDs with Ge core was increased. The results will lead to the development of high efficient light-emitting devices using Si-based QDs.

We formed high-density Si quantum dots (Si-QDs) with undoped and P-doped Ge cores on thermally-grown SiO 2 by controlling low pressure chemical vapor depositions of Si and Ge. Doping into the Ge core was carried out during selective-growth of Ge on pre-grown Si-QDs. From hard x-ray photoelectron spectroscopy measurements, we confirmed phosphorus incorporation into the Ge core, where phosphorus donor concentration in the Ge core was roughly estimated to be ∼0.09 at%. When the surfaces of Si-QDs with undoped and P-doped Ge cores were scanned with an Rh-coated tip biased at 0 V, the surface potential of Si-QDs with P-doped Ge cores were increased by ∼30 mV, while that of Si-QDs with undoped Ge cores remained unchanged. These results indicate that an electron was extracted from the conduction band of the Ge core due to a phosphorus donor. In the current images measured with the Rhcoated tip, the current level of Si-QDs with P-doped Ge cores on n-Si(100) substrates was higher than that of Si-QDs with undoped Ge cores. This result indicates that phosphorus donor can contribute to an increase in the electron injection rate from the Si-substrate.

We have demonstrated formation of Fe–silicide nanodots (NDs) on SiO2 by exposing Fe NDs to SiH4. The Fe NDs were formed by exposing ultrathin Fe film deposited on SiO2 to remote H2–plasma. After SiH4 exposure at 400°C, formation of Fe–silicide NDs with an areal dot density over 1011 cm−2 was confirmed. Photoluminescence from the Fe–silicide NDs was observable at room temperature in the near-infrared, being attributed to radiative recombination between quantized states in the NDs. The results will lead to the development of Si-based light-emitting devices that are highly compatible with Si ultralarge-scale-integration processing.

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