Direct growth and size tuning of InAs/GaAs quantum dots on transferable silicon nanomembranes for solar cells application

In this paper we show for the first time the possibility to direct grow and tune the
size and optical properties of high quality InAs/GaAs quantum dots on transferable crystalline silicon nanomembranes. The transferable silicon nanomembranes have been grown via in-situ H2 prebake of porous silicon in Ultra High
Vacuum Chemical vapour Deposition (UHV-CVD) reactor. Flat and continuous
transferable crystalline nanomembranes with thicknesses below 30 nm have been
obtained. The mechanical strain in the silicon nanomembranes has been tuned via
sintering temperature between 900 and 1100 C for the direct crystalline growth of
transferable InAs/GaAs (QDs)/Si foils. The size and band gap energy of these
InAs/GaAs quantum dots are tuned via strain engineering in silicon nanomembranes. Several advanced techniques such as Scanning Electron Microscopy
(SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), X-Ray
Diffraction (XRD), Photoluminescence (PL) spectroscopy are used to investigate
the structural and optical properties of transferable silicon nanomembranes and
the grown InAs/GaAs QDs. High quality InAs/GaAs QDs with tuned sizes
grown on flat and continuous transferable crystalline nanomembranes have been
obtained. The obtained results have shown that this novel process allows the
growth of well separated InAs/GaAs QDs with well defined shape, high density
around 2 9 1010/cm2 and a well controlled size variation as function of the substrate strain between 2 and 10 nm. The high quality of the structural and optical
properties of the InAs/GaAs QDs monolithically grown on a transferable Si
nanomembranes and its compatibility with standard Si solar cells technologies
offer a great opportunity for growing a cheap and high performance InAs/GaAs
quantum dots/Si third generation solar cells and microelectronic devices.