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Structural and optical properties of germanium nanostructures on Si(100) and embedded in high-k oxides.

Ray SK, Das S, Singha RK, Manna S, Dhar A - Nanoscale Res Lett (2011)

Bottom Line: The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented.The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented.The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Meteorology, Indian Institute of Technology Kharagpur 721302, India. physkr@phy.iitkgp.ernet.in.

ABSTRACT
The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented. The infrared photoluminescence (PL) signal from Ge islands has been studied at a low temperature. The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented. The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied. Transmission electron micrographs have revealed the formation of isolated spherical Ge nanocrystals in high-k oxide matrix of sizes ranging from 4 to 18 nm. Embedded nanocrystals in high band gap oxides have been found to act as discrete trapping sites for exchanging charge carriers with the conduction channel by direct tunneling that is desired for applications in floating gate memory devices.

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10 K photoluminescence spectra of Ge islands grown on Si substrate for sample (a) GS-1 and (b) GS-2.
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Figure 2: 10 K photoluminescence spectra of Ge islands grown on Si substrate for sample (a) GS-1 and (b) GS-2.

Mentions: The strength of no-phonon transitions and the overlap of electron and hole wave functions can be enhanced in Si/Ge nanostructures, but their quantum efficiency remains orders of magnitude below that of direct optical transitions. Figure 2 shows the 10 K PL spectra of self-assembled Ge QDs grown at 500°C for (a) 2 min (sample 'GS-1') and (b) 5 min (sample 'GS-2'). Broad PL peaks are observed around 0.755 and 0.804 eV for samples grown for 5 and 2 min, respectively. The observed broad PL signal from Ge/Si islands is associated with the radiative carrier recombination at sharp Ge/Si interface that exhibits type-II band alignment, with a small barrier for electrons and deep potential wells for the holes confined within the Ge islands [9]. Due to lower height (7 to 18 nm) of the islands, the PL peak of 2 min sample is blue shifted compared to sample grown for 5 min. Another cause for the shift may be due to the intermixing of Si and Ge for longer time (5 min) deposition of Ge, which reduces the band offset between islands and Si interface.


Structural and optical properties of germanium nanostructures on Si(100) and embedded in high-k oxides.

Ray SK, Das S, Singha RK, Manna S, Dhar A - Nanoscale Res Lett (2011)

10 K photoluminescence spectra of Ge islands grown on Si substrate for sample (a) GS-1 and (b) GS-2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211282&req=5

Figure 2: 10 K photoluminescence spectra of Ge islands grown on Si substrate for sample (a) GS-1 and (b) GS-2.
Mentions: The strength of no-phonon transitions and the overlap of electron and hole wave functions can be enhanced in Si/Ge nanostructures, but their quantum efficiency remains orders of magnitude below that of direct optical transitions. Figure 2 shows the 10 K PL spectra of self-assembled Ge QDs grown at 500°C for (a) 2 min (sample 'GS-1') and (b) 5 min (sample 'GS-2'). Broad PL peaks are observed around 0.755 and 0.804 eV for samples grown for 5 and 2 min, respectively. The observed broad PL signal from Ge/Si islands is associated with the radiative carrier recombination at sharp Ge/Si interface that exhibits type-II band alignment, with a small barrier for electrons and deep potential wells for the holes confined within the Ge islands [9]. Due to lower height (7 to 18 nm) of the islands, the PL peak of 2 min sample is blue shifted compared to sample grown for 5 min. Another cause for the shift may be due to the intermixing of Si and Ge for longer time (5 min) deposition of Ge, which reduces the band offset between islands and Si interface.

Bottom Line: The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented.The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented.The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Meteorology, Indian Institute of Technology Kharagpur 721302, India. physkr@phy.iitkgp.ernet.in.

ABSTRACT
The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented. The infrared photoluminescence (PL) signal from Ge islands has been studied at a low temperature. The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented. The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied. Transmission electron micrographs have revealed the formation of isolated spherical Ge nanocrystals in high-k oxide matrix of sizes ranging from 4 to 18 nm. Embedded nanocrystals in high band gap oxides have been found to act as discrete trapping sites for exchanging charge carriers with the conduction channel by direct tunneling that is desired for applications in floating gate memory devices.

No MeSH data available.


Related in: MedlinePlus