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Heavily p-type doped Ge layers were fabricated by 100 keV Ga implantation and subsequent flash lamp annealing for 3 ms in the temperature range between 700 and 900 °C. For comparison, some samples were annealed in a rapid thermal processor for 60 s. Ga fluences of 2×1015, 6×1015, and 2×1016 cm-2 were chosen in order to achieve Ga peak concentrations ranging from values slightly below the equilibrium solid solubility limit of 4.9×1020 cm-3 up to 3.5×1021 cm-3 which corresponds to a maximum Ga content of about 8 at. %. The structure of the doped layer and the Ga distribution were investigated by Rutherford backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy, and secondary ion mass spectrometry. Temperature dependent Hall effect measurements were carried out in order to determine the electrical properties of the Ga-doped Ge layers. It is shown that by flash lamp annealing Ga diffusion into the bulk can be completely avoided and the Ga loss by outdiffusion from the surface is reduced. The lowest sheet resistance of 36 Ω/sq. was achieved for the medium Ga concentration annealed at 900 °C. The best Ga activation values are 73%, 60%, and 24% for the three Ga fluences under investigation. The Ga activation is correlated with the layer regrowth. Incomplete epitaxial regrowth as observed in some samples leads to lower activation. [ABSTRACT FROM AUTHOR]

Using combined electroluminescence (EL) and photoluminescence (PL) studies we establish that the energy transfer process from the Er3+ to the Ge-related oxygen-deficiency centers (GeODCs) plays the key role in enhancing the 404 nm EL intensity in Ge-rich SiO2. Er doping induced structural modification does not appear to be relevant, which is deduced from the 404 nm PL quenching with increasing Er concentration, implying a gradual loss of GeODCs. In contrast to PL, the 404 nm EL intensity increases by 0.3% Er doping followed by a gradual decrease in intensity for higher Er concentrations, which is described in terms of a competition between the energy transfer process and the gradual segregation of Er due to the destruction of GeODCs with Er doping. This fact is further discussed in the light of ab initio molecular orbital calculations. [ABSTRACT FROM AUTHOR]

Using combined microstructural and electroluminescence (EL) investigations of the Er-doped Ge-rich SiO2 layers, it is established that the Ge-related oxygen-deficiency centers (GeODCs), which are associated with the 407 nm light emission, are situated at the Ge nanocrystal/SiO2 interface. Electrically driven energy transfer from the Er3+ to GeODCs causes an increase in the 407 nm EL intensity. It reaches a maximum before quenching with increasing Er concentration due to the crystalline-to-amorphous transition of Ge nanocrystals. Ge concentration dependent quenching of the maximum EL intensity and the peak shifting toward higher Er concentration are discussed in terms of the reduction of the surface-to-volume ratio with increasing nanocrystal size. [ABSTRACT FROM AUTHOR]

Abstract: Nanometer-thick silicon-germanium-on-insulator (SGOI) structures have been produced by the implantation of Ge+ ions into thermally grown SiO2 layer and subsequent hydrogen transfer of silicon film on the Ge+ ion implanted substrate. The intermediate nanometer-thick Ge layer has been formed as a result of the germanium atom segregation at the Si/SiO2 bonding interface during annealing at temperatures 800–1100 оС. From a thermodynamic analysis of Si/Ge/SiO2 system, it has been suggested that the growth of the epitaxial Ge layer is provided by the formation of a molten layer at the Si/SiO2 interface due to the Ge accumulation. The effect of germanium on the hole mobility in modulation-doped heterostructures grown over the 3–20nm thick SGOI layers was studied. An increase in the Hall hole mobility in SGOI-based structures by a factor of 3–5 was obtained in comparison with that in respective Ge-free SOI structures. [Copyright &y& Elsevier]

Systematic features of endotaxial growth of intermediate germanium layers at the bonding interface in the silicon-on-insulator structure consisting of buried SiO2 layer implanted with Ge+ ions are studied in relation to the annealing temperature. On the basis of the results for high-resolution electron microscopy and thermodynamic analysis of the Si/Ge/SiO2 system it is assumed that the endotaxial growth of the Ge layer occurs via formation of a melt due to enhanced segregation and accumulation of Ge at the Si/SiO2 interface. Effect of germanium at the bonding interface on the Hall mobility of holes in silicon layers with nanometer-scale thickness is studied. It is found that the structures including the top silicon layer with the thickness 3–20 nm and incorporating germanium feature the hole mobility that exceeds by a factor of 2–3 the hole mobility in corresponding Ge-free silicon-on-insulator structures. [ABSTRACT FROM AUTHOR]

The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator structures are studied. It is shown that, under conditions of high-temperature (1100°C) annealing, germanium nanocrystals are not formed, while the implanted Ge atoms segregate at the Si/SiO2 bonding interface. It is established that, in this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. In this situation, the main type of traps is the positive-charge traps; their effect is interpreted in the context of an increase in the surface-state density due to the formation of weaker Ge-O bonds. It is found that the slope of the drain-gate characteristics of the back MIS transistors increases; this increase is attributed to an increased mobility of holes due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL), Raman scattering, and the Rutherford backscattering of α-particles were used to study the formation of the centers of radiative-recombination emission in the visible region of the spectrum on annealing of the SiO[sub 2] layers implanted with Ge ions. It was found that the Ge-containing centers were formed in the as-implanted layers, whereas the stages of increase and decrease in the intensities of PL bands were observed following an increase in the annealing temperature to 800°C. The diffusion-related redistribution of Ge atoms was observed only when the annealing temperatures were as high as 1000°C and was accompanied by formation of Ge nanocrystals. However, this did not give rise to intense PL as distinct from the case of Si-enriched SiO[sub 2] layers subjected to the same treatment. It is assumed that, prior to the onset of Ge diffusion, the formation of PL centers occurs via completion of direct bonds between the neighboring excess atoms, which gives rise to the dominant violet PL band (similar to the PL of O vacancies in SiO[sub 2]) and a low-intensity long-wavelength emission from various Ge-containing complexes. The subsequent formation of centers of PL with λ[sub m] ∼ 570 nm as a result of anneals at temperatures below 800°C is explained by agglomeration of bonded Ge atoms with formation of compact nanocrystalline precipitates. The absence of intense PL following the high-temperature anneals is believed to be caused by irregularities in the interfaces between the formed Ge nanocrystals and the SiO[sub 2] matrix. [ABSTRACT FROM AUTHOR]

Superconducting Ga-rich layers in Ge are fabricated by Ga implantation through a thin Si02 cover layer. After annealing in a certain temperature window, Ga accumulation at the SiC/Ge interface is observed. However, no Ga-containing crystalline phases are identified. Thus it is suggested that the volatile Ga is stabilized in an amorphous mixture of all elements available at the interface. Electrical transport measurements reveal p-type metallic conductivity and superconducting transition. The superconducting properties of the samples with high Ga concentration at the interface change dramatically with etching the amorphous surface layer. A critical temperature of 6 K is measured before, whereas after etching it drops below 1 K. Therefore, one can conclude that the superconducting transport is based on two different layers: a Ga-rich amorphous phase at the interface and a heavily Ga-doped Ge layer. Finally, the comparison of the transport properties of Ga-rich Ge with those of Si demonstrates distinct differences between the interface layers and even the deeper-lying doped regions. [ABSTRACT FROM AUTHOR]