I.A. Morozov

Fabrication of Hybrid Nanostructures via Nanoscale Laser-Induced Reshaping for Advanced Light Manipulation

Ordered hybrid nanostructures for nanophotonics applications are fabricated by a novel approach via femtosecond laser melting of asymmetric metal-dielectric (Au/Si) nanoparticles created by lithographical methods. The approach allows selective reshaping of the metal components of the hybrid nanoparticles without affecting the dielectric ones and is applied for tuning of the scattering properties of the hybrid nanostructures in the visible range.

Si doped GaP layers grown on Si wafers by low temperature PE-ALD

Low-temperature plasma enhanced atomic layer deposition (PE-ALD) was successfully used to grow silicon (Si) doped amorphous and microcrystalline gallium phosphide (GaP) layers onto p-type Si wafers for the fabrication of n-GaP/p-Si heterojunction solar cells. PE-ALD was realized at 380 °C with continuous H2 plasma discharge and the alternate use of phosphine and trimethylgallium as sources of P and Ga atoms, respectively. The layers were doped with silicon thanks to silane (SiH4) diluted in H2 that was introduced as a separated step. High SiH4 dilution in H2 (0.1%) allows us to deposit stoichiometric GaP layers. Hall measurements performed on the GaP:Si/p-Si structures reveal the presence of an n-type layer with a sheet electron density of 6–10 × 1013 cm−2 and an electron mobility of 13–25 cm2 V−1 s−1 at 300 K. This is associated with the formation of a strong inversion layer in the p-Si substrate due to strong band bending at the GaP/Si interface. GaP:Si/p-Si heterostructures exhibit a clear photovoltaic effect, with the performance being currently limited by the poor quality of the p-Si wafers and reflection losses at the GaP surface. This opens interesting perspectives for Si doped GaP deposited by PE-ALD for the fabrication of p-Si based heterojunction solar cells.

Low temperature plasma enhanced deposition of GaP films on Si substrate

Amorphous and microcrystalline GaP films were deposited on Si substrates by time modulated plasma enhanced deposition from trimethylgallium and phosphine using constant hydrogen plasma at a temperature of 250–380 °C. Amorphous GaP films obtained at constant low radio-frequency (RF) power (20 W) mode exhibit the broad feature at 350–360 cm−1 and a shoulder at 370–390 cm−1 in Raman spectra. Amorphous films have smooth surface with root-mean-square (RMS) roughness decreasing from 0.9 to 0.2 nm with increasing deposition temperature from 250 to 380 °C. Small amounts of 3–5 nm GaP nanocrystal inclusions in the amorphous matrix are formed at 380 °C. An increase of RF power to 100 W during Ga and P deposition steps leads to the formation of a GaP crystalline phase as confirmed by transmission electron microscopy. Two peaks in the Raman spectra at 365 and 402 cm−1, which correspond to GaP TO-LO duplet, were observed in this case. However, the microcrystalline GaP layers have rough surface with RMS roughness of 6 ...

Low temperature plasma enhanced deposition approach for fabrication of microcrystalline GaP/Si superlattice

A plasma technology approach to grow microcrystalline GaP/Si superlattices was explored. The layers of GaP were grown using time modulated plasma enhanced deposition (atomic layer deposition approach), while Si layers were grown using the conventional plasma enhanced chemical vapor deposition mode with high hydrogen dilution. The (3 nm)GaP/(2 nm)Si superlattices were formed on Si and GaP substrates either by the growth of an amorphous GaP/Si multilayer structure followed by thermal annealing at 450–900 °C or by growth of a microcrystalline GaP/Si superlattice at temperatures not exceeding 400 °C. A quantum confinement effect of thin 2 nm Si layers was demonstrated by the appearance of a peak at 500 cm−1 in Raman spectra. The crucial role of hydrogen behavior in Si crystallization and void formation during the annealing of amorphous and growth of microcrystalline GaP/Si structures was demonstrated.

Defect properties of InGaAsN layers grown as sub-monolayer digital alloys by molecular beam epitaxy

The defect properties of InGaAsN dilute nitrides grown as sub-monolayer digital alloys (SDAs) by molecular beam epitaxy for photovoltaic application were studied by space charge capacitance spectroscopy. Alloys of i-InGaAsN (Eg = 1.03 eV) were lattice-matched grown on GaAs wafers as a superlattice of InAs/GaAsN with one monolayer of InAs (<0.5 nm) between wide GaAsN (7–12 nm) layers as active layers in single-junction solar cells. Low p-type background doping was demonstrated at room temperature in samples with InGaAsN layers 900 nm and 1200 nm thick (less 1 × 1015 cm−3). According to admittance spectroscopy and deep-level transient spectroscopy measurements, the SDA approach leads to defect-free growth up to a thickness of 900 nm. An increase in thickness to 1200 nm leads to the formation of non-radiative recombination centers with an activation energy of 0.5 eV (NT = 8.4 × 1014 cm−3) and a shallow defect level at 0.20 eV. The last one leads to the appearance of additional doping, but its concentration i...

Reversible and non-reversible tuning of hybrid optical nanoresonators

Recently, we have proposed a novel approach for fabrication of asymmetric metal-dielectric (hybrid) nanoparticles via combination of standard lithography processes and femtosecond laser reshaping of a metal component of the nanoparticle. Here, we study the influence of the geometrical parameters of the hybrid nanoparticle on the reshaping process. We also demonstrate non-reversible tuning of light absorbtion and reversible tuning of transmittance of the hybrid nanostructures in a wide range.