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Spectral dependences of lateral photoconductivity of Si1−xGex heterostructures with Ge nanoislands were investigated at 77 and 290 K. It is supposed that the photocurrent in the range 0.81–1.02 eV at 290 K is conditioned by a nonequilibrium carrier generated by interband transitions in Ge nanoislands. Si1−xGex heterostructures with Ge nanoislands showed lateral photocurrent in the range from 0.32 to 1.2 eV at 77 K. Such a photocurrent is explained by hole transitions from the localized states of light and heavy holes in Ge nanoislands into the delocalized states of the valence band. It was found that the valence bandgap offset of the heterojunction between the nanoislands and strained c-Si surrounding was 0.48 eV.

The results of the experimental studies of the effect of nanoislands on the lateral photoconductivity in structures with Ge nanoislands formed on the SiOx layer using molecular beam epitaxy are reported. It is shown that nanoislands increase the surface recombination rate and affect the fundamental absorption edge of c-Si. The generation of lateral photocurrent in the range 0.8 – 1.0 eV was observed due to transitions between tails in the density of states of the near-surface c-Si, which is described by Urbach dependence. It was shown that the absorption spectrum of nanoislands is typical for the disordered Ge and is due to transitions between density-of-states tails of the valence and conductance bands. The mechanism is proposed of lateral photoconductivity involving the non-equilibrium charge carriers, generated in Ge nanoislands. It is suggested that the optical absorption and lateral photocurrent in Ge-SiOx-Si structures are affected by fluctuations of the surface potential in the near-surface region of c-Si, fluctuations of the Si band gap width and by effects of disorder in Ge nanoislands.

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Low-frequency noise of the structures with Ge-nanoclusters of rather high surface density grown on the oxidized silicon surface is investigated for the first time. It was revealed that the 1/f γ noise, where γ is close to unity, is the typical noise component. Nevertheless, the 1/f γ noise sources were found to be distributed nonuniformly upon the oxidized silicon structure with Ge-nanoclusters. The noise features revealed were analyzed in the framework of widely used noise models. However, the models used appeared to be unsuitable to explain the noise behavior of the structures studied. The physical processes that should be allowed for to develop the appropriate noise model are discussed.