Metal-induced
crystallization of amorphous silicon is a promising
technique for developing high-quality and cheap optoelectronic devices.
Many attempts tried to enhance the crystal growth of polycrystalline
silicon via aluminum-induced crystallization at different annealing
times and temperatures. In this research, thin films of aluminum/silicon
(Al/Si) and aluminum/silicon/tin (Al/Si/Sn) layers were fabricated
using the thermal evaporation technique with a designed wire tungsten
boat. MIC of a:Si was detected at annealing temperature of 500 °C
using X-ray diffraction, Raman spectroscopy, and field emission scanning
electron microscopy. The crystallinity of the films is enhanced by
increasing the annealing time. In the three-layer thin films, MIC
occurs because of the existence of both Al and Sn metals forming highly
oriented (111) silicon. Nanocrystalline silicon with dimensions ranged
from 5 to 300 nm is produced depending on the structure and time duration.
Low surface reflection and the variation of the optical energy gap
were detected using UV–vis spectroscopy. Higher conductivities
of Al/Si/Sn films than Al/Si films were observed because of the presence
of both metals. Highly rectifying ideal diode manufactured from Al/Si/Sn
on the FTO layer annealed for 24 h indicates that this device has
a great opportunity for the optoelectronic device applications.
Solubility of Sn in Ge network gives it a preference
for photonic
applications, because of the direct transition in GeSn alloy. Here,
we employed the metal-induced crystallization (MIC) process of amorphous
Ge and Si via Sn as a novel mechanism to incorporate Sn inside Ge
and Si networks. (Al/Si/Sn/Ge/Sn) and (Al/Ge/Sn/Ge/Sn) multilayers
are deposited by thermal vacuum evaporation on different substrates.
The devices are annealed under low vacuum at 500 °C to incorporate
the oxygen for band-gap tuning. The structure of Ge-doped nanocrystals
is investigated. The direct transition and band-gap values have been
estimated using diffuse reflectance spectroscopy and photoluminescence
(PL) measurements. PL indicated that the junctions have emissions
from visible to NIR regions that make them promising as optically
pumped white-light sources as well as waveguide applications, and
the impact of the base substrate on enhancing the emission has been
investigated via PL measurements. Electroluminescence measurements
show that the prepared heterostructures on fluorine-doped tin oxide
(FTO) substrate have sharp random lasing spikes over the range of
PL samples spectra as the sample can lase randomly by light scattering
through the Ge-doped nanocrystalline materials. The charge carrier
lifetime measurements show high lifetime for the prepared sample.
These give them the chance to be a candidate for white-light random
laser diode applications.
Solubility of Sn in Ge has the most impact in the emission characteristics of direct band gap GeSn alloy. Here, we employed the metal induced crystallization (MIC) process of amorphous Ge and Si via Sn as a novel mechanism to incorporate Sn inside Ge and Si networks. (Al/Si/Sn/Ge/Sn) and (Al/Ge/Sn/Ge/Sn) multilayers are deposited by thermal vacuum evaporation on different substrates. The devices are annealed under low vacuum at 500 ºC. The Ge doped nanocrystals structure is investigated. The direct transition and band gap values have been estimated using diffuse reflectance spectroscopy and Photoluminescence (PL) measurements. PL indicted that the junctions have emissions from visible to NIR regions that make them promise in white light laser sources as well as waveguiding applications. Charge carrier lifetime and EL measurements show high lifetime and very sharp emission, respectively indicating that the prepared structure is a candidate for white laser diode applications.
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