Abstract
In this work we prepared films of amorphous germanium nanoparticles embedded in SiO2 deposited by magnetron sputtering on Si and quartz heated substrates at 300, 400 and 500 °C. Structure, morphology, optical, electrical and photoconduction properties of all films were investigated. The Ge concentration in the depth of the films is strongly dependent on the deposition temperature. In the films deposited at 300 °C, the Ge content is constant in the depth, while films deposited at 500 °C show a significant decrease of Ge content from interface of the film with substrate towards the film free surface. From the absorption curves we obtained the Ge band gap of 1.39 eV for 300 °C deposited films and 1.44 eV for the films deposited at 500 °C. The photocurrents are higher with more than one order of magnitude than the dark ones. The photocurrent spectra present different cutoff wavelengths depending on the deposition temperature, i.e. 1325 nm for 300 °C and 1267 nm for 500 °C. These films present good responsivities of 2.42 AW−1 (52 μW incident power) at 300 °C and 0.69 AW−1 (57 mW) at 500 °C and high internal quantum efficiency of ∼445% for 300 °C and ∼118% for 500 °C.
Highlights
In the last decade, many research groups have paid attention on amorphous germanium nanoparticles (Ge-NPs) embedded in different oxide matrices because of their attractive electrical and optical properties which are suitable for different applications like photo-detectors[1,2,3], solar cells[4], light-emitting diodes[5], memory devices[6], MOSFET transistors[7,8] and lithium-ion batteries with high charge-discharge rate[9,10]
These spectra are deconvoluted by five maxima positioned at about similar wavelengths with different relative intensities depending on the deposition temperature
The other maxima and shoulders situated below 1100 nm can be attributed to photo-effects in Ge-NPs:SiO2 films, the main contribution being due to Ge related defects acting as traps
Summary
Many research groups have paid attention on amorphous germanium nanoparticles (Ge-NPs) embedded in different oxide matrices because of their attractive electrical and optical properties which are suitable for different applications like photo-detectors[1,2,3], solar cells[4], light-emitting diodes[5], memory devices[6], MOSFET transistors[7,8] and lithium-ion batteries with high charge-discharge rate[9,10] This effort has the main aim to extend the sensitivity domain of photodetectors toward near infrared (NIR) and to develop the optoelectronics in this wavelength range as Si based photodetectors are usually limited to 1.1–1.2 μm. This approach brings important contribution to the effort of structuring Ge-NPs in SiO2 thin films at lower temperature (during deposition) in the aim of using the performance of these materials towards integrated optoelectronics
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