Alexander V. Shevlyagin

Room temperature 1.5 μm light-emitting silicon diode with embedded β-FeSi2 nanocrystallites

Light-emitting silicon diode structures with embedded β-FeSi2 nanocrystallites have been fabricated using solid phase epitaxy and a combination of reactive deposition and solid phase epitaxy. Electroluminescence (EL) of the structures was studied over various temperatures and current densities under forward and reverse biases. The structures with nanocrystallites formed by the combined method exhibited EL at temperatures below 70 K only, suggesting the presence of a high concentration of defects—non-radiative centers. High-quality defect-free structures with nanocrystallites formed by solid phase epitaxy revealed intensive room temperature EL in energy range 0.76–1.08 eV at current densities as low as 1 A/cm2.

Characterization of the silicon/β-FeSi2 nanocrystallites heterostructures for the NIR photodetection at low temperature

Using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, p-Si/β-FeSi2 nanocrystallites/n-Si(001) diode structure was fabricated. The diode exhibited a current responsivity of 15 mA/W and external quantum efficiency of about 1% at a wavelength of 1300 nm at 120 K without bias and 200 mA/W and 10%, respectively, at −30 V. The device specific detectivity calculated at 120 K in zero bias conditions of 2.1 × 1011 cmHz1/2/W at a wavelength of 1.3 µm is the highest ever reported for Si/β-FeSi2 systems. The Franz–Keldysh effect gives grounds for applying such systems not only for the development of optrons but also for that of electro-optical modulators.

On the way to enhance the optical absorption of a-Si in NIR by embedding Mg2Si thin film

Mg2Si thin film was embedded in amorphous silicon matrix by solid phase epitaxy. The structure and optical properties were investigated by electron energy loss, X-ray photoelectron, Raman, and photo thermal deflection spectroscopy measurements. It was found that in the photon energy range of 0.8–1.7 eV, the light absorption of the structure with magnesium silicide (Mg2Si) film embedded in a-Si(i) matrix is 1.5 times higher than that for the same structure without Mg2Si.

VIS-NIR-SWIR multicolor avalanche photodetector originating from quantum-confined Stark effect in Si/β-FeSi2/Si structure

A Si n-i-p avalanche photodetector with embedded β-FeSi2 nanocrystals was developed. The device showed an ultrabroadband photoresponse from the visible (400 nm) to short-wavelength infrared (1800 nm) ranges. Specific detectivity at zero bias conditions reaches 2 × 109 cmHz1/2/W at 1300 nm and 2 × 108 cmHz1/2/W above 1400 nm at room temperature. Observed quantum-confined Stark effect together with avalanche multiplication resulted in a simultaneous two orders of magnitude increase in the photoresponse and spectral sensitivity expanding to 1800 nm when the device is operated in avalanche mode. The application fields of the proposed photodetector potentially include integrated Si photonics and multicolor photodetection; the quantum-confined Stark effect gives grounds for the development of fast-operated electro-optical modulators.

Phase composition evolution of iron silicide nanocrystals in the course of embedding into monocrystalline silicon

Evgeniy A. Chusovitin, Dmitry L. Goroshko, Sergey A. Dotsenko, Alexander V. Shevlyagin, Nikolay G. Galkin and Anton K. Gutakovskii 1Institute of Automation and Control Processes FEB RAS, 5 Radio St., 690041 Vladivostok, Russia 2Far Eastern Federal University, School of Natural Sciences 8 Sukhanova St., 690950 Vladivostok, Russia 3Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia.

Solid phase epitaxy formation of silicon-GaSb based heterostructures

A double-layer heterostructure with embedded into single-crystalline silicon matrix nanocrystallites of gallium antimonide was grown. GaSb was formed by solid phase epitaxy method using Ga-Sb stoichiometric mixture of 2-nm-thick and a stepped annealing from 200 to 500 °C. The obtained nanocrystallites have a concentration of 7.1×10 cm, a height of 4.6 nm and lateral dimensions of 16–20 nm. The GaSb nanocrystallites were covered with silicon layer using molecular beam epitaxy in two stage: 40-nm-thick at 300 °C followed by 60-nm-thick at 500 °C.

Extended near-IR Spectral Sensitivity and Electroluminescence Properties of Silicon Diode Structure with GaSb/Si Composite Layer

An array of GaSb nanocrystallites (NCs) was formed on Si(001) substrate by solid-phase epitaxy at 500 °C. Owing to the embedded GaSb NCs, p+‑Si/NC‑GaSb/n‑Si mesa diode spectral sensitivity has extended up to 1.6 µm at room temperature, and its integral sensitivity has increased by 4–5% in the wavelength range of 1200–1600 nm, as compared to a conventional Si diode. This result was achieved by embedding only 10 nm of GaSb in the form of NCs inside a silicon matrix. In addition, we could obtain a significant electroluminescence (EL) signal at 120 K in a very wide wavelength range from 1.3 to 2.1 µm (0.95–0.59 eV). The EL spectrum has a broad maximum at 1700 nm (0.73 eV). The threshold pumping current density was as low as 0.75 A/cm2.

Formation of Bulk and Nanocrystallite Layers of GaSb on Silicon

Formation of GaSb by means of solid phase epitaxy of amorphous Ga:Sb (1:1) layer on Si (001) substrate at 500 °C has been studied. At amorphous layer thickness of 16 nm, a continuous nanocrystalline layer of GaSb was formed. Decreasing of amorphous layer thickness up to 0.8 nm resulted in formation of separated GaSb nanocrystallites (NCs), which had a mean lateral size of 30–80 nm and mean height of 2–3 nm, while their concentration reached 3×109 cm-2. Atomic force microscopy and low energy electron diffraction data showed that GaSb NCs could be fully embedded into silicon lattice by deposition of 25-nm-thick silicon layer at 650 °C. Nevertheless, on a surface of the silicon layer, some holes have been formed because of NCs moving toward to the surface. The holes formation can be almost completely suppressed by deposition of additional 25-nm-thick silicon layer at 500 °C – so-called “stop-layer”.

Non-doped and doped Mg stannide films on Si(111) substrates: Formation, optical, and electrical properties

Thin (45–50 nm) non-doped and doped (by Sb and Al) polycrystalline Mg stannide films consisting mainly of Mg2Sn semiconductor phase and containing small quantity of Mg2Si phase have been grown by multiple layer deposition at room temperature and single step annealing at 150 °C of the (Sn–Mg) bi-layers on Si(111) n-type wafers with 7.5 Ωcm resistivity. Optical spectroscopy data have shown that the grown Mg stannide films is a semiconductor with direct band gap of 0.17 ± 0.03 eV, with second and third direct interband transitions at 0.34 ± 0.02 and 0.45 ± 0.04 eV. An undispersed refraction index: n0 = 3.78 ± 0.06 was calculated from phonon energy dependence of the refraction index of the grown films in the 0.12–0.20 eV energy range. Temperatures dependent Hall effect measurements have revealed about 0.28 eV electrical band gap value in the films.