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THE INFLUENCE OF THE ERBIUM ATOM ON THE OPTICAL PROPERTIES OF
EPITASIAL SILICON FILMS
Bazarbaeva H.
Kudainazarov A.
Saburov N.
Sharibaev M.
Karakalpak state univesity named after Berdakh.
https://doi.org/10.5281/zenodo.14491942
Abstrct. The results of growing erbium-doped epitaxial silicon layers using two different
growth modes: conventional molecular beam epitaxy (MBE) and solid-phase epitaxy (SPE) are
presented. It has been shown that an erbium-doped silicon layer, when deposited by SPE onto a
cold substrate and subsequent annealing, exhibits more intense photoluminescence at a
wavelength of 1.54 µm than layers grown by MBE.
Key words: photoluminescence, epitaxial film, deformation, intensity, mechanical stress.
ВЛИЯНИЕ АТОМА ЭРБИЯ НА ОПТИЧЕСКИЕ СВОЙСТВА ЭПИТАЗИАЛЬНЫХ
КРЕМНИЕВЫХ ПЛЕНОК
Аннотация. Представлены результаты выращивания эпитаксиальных слоев
кремния, легированных эрбием, с использованием двух различных режимов роста:
традиционной молекулярно-лучевой эпитаксии (МЛЭ) и твердофазной эпитаксии (ТФЭ).
Показано, что слой кремния, легированный эрбием, нанесенный методом ТФЭ на
холодную подложку и подвергнутый последующему отжигу, проявляет более интенсивную
фотолюминесценцию на длине волны 1,54 мкм, чем слои, выращенные методом МЛЭ.
Ключевые слова: фотолюминесценция, эпитаксиальная пленка, деформация,
интенсивность, механическое напряжение.
Introduction.
The growing number of studies of erbium-doped silicon is associated with
the possibility of using this material to create silicon optoelectronic devices at a wavelength of
1.54 µm [1]. One of the conditions for the successful implementation of silicon device structures
is to achieve a high content of optically active centers associated with erbium. When doping silicon
with erbium using ion implantation, high-energy ions (0.5–5 MeV) are used.
This leads to the formation of defects that are partially preserved even after prolonged
annealing and lead to the precipitation of rare-earth impurities [2]. In ion implantation, as in other
doping methods, optically inactive silicide compounds are formed as a result of the interaction of
erbium and silicon atoms.
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It was found that in order to suppress the formation of erbium precipitates and erbium
silicides, it is necessary to carry out the doping process at low temperatures and dope the silicon
layers with oxygen to form optically active centers, including Er
3+
ions [3].
Using the molecular beam epitaxy (MBE) method with the evaporation of silicon and
erbium, it is possible to grow layers with a total erbium concentration of up to 10
22
cm
−3
[4].
owever, the intensity of photoluminescence in layers with an erbium concentration greater than 10
18
cm
−3
begins to weaken, which is probably due to the formation of defects in the crystal structure
[4- 6].
Another method that allows growing heavily doped silicon layers is solid-phase epitaxy
(SPE). The growth process in it is carried out in two stages: deposition of the layer at low
temperatures, when the segregation of the impurity is kinetically suppressed, and subsequent
annealing of the amorphous silicon film [6].
The purpose of this work is to study the possibility of growing heavily erbium-doped
silicon layers by SPE, exhibiting photoluminescence at a wavelength of 1.54 µm.
Experimental technique
The growth of erbium-doped silicon layers was carried out in an ultra-high-vacuum MBE
setup using the device shown in Fig.1 [7]. Si was evaporated from a sublimation source in the form
of a rectangular bar heated by passing current, and Er was also evaporated from a sublimation
source cut from metal foil.
The substrate was a rectangular silicon plate cut along the (100) or (111) plane from KDB-
12 single-crystal silicon. Like the sources, it was heated by passing current.
After annealing the substrate at T=1250
◦
C for 10 min, silicon layers were grown either by
MBE at a substrate temperature of 500
◦
C or by SPE on a heated substrate with subsequent
annealing min situ.
The PL spectra of the structures were measured at a temperature of 77 K using a BOMEM
DA3 Fourier spectrometer with a resolution of 1 cm−1 under pumping by an Ar
+
laser (with a
wavelength of λ=514.5 nm) with a power of 80 mW from the side of the epitaxial layer. The
structure of the layers was studied by electron diffraction.
The photoluminescence spectrum of this structure, measured at liquid nitrogen
temperature, is shown in Fig. 2. A broad band with a maximum at 6500 cm
−1
is characteristic of
the PL of the Er
3+
ion in Si:Er/Si structures obtained by sublimation MBE with a metallic erbium
source and containing a higher (compared to the erbium content) concentration of oxygen and
carbon.
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Fig. 1. PL spectrum of the structure grown by MBE. The spectrum was recorded at T=77
K and argon laser pump power P=80 mW.
The photoluminescence spectrum of erbium in an epitaxial silicon layer grown in the SPE
mode is shown in Fig. 4. The spectrum contains an intense series of narrow luminescence lines
related to the
4
II
3/2
→
4
II
5/2
transition in the 4f shell of the Er
3+
ion in the known isolated emitting
center with cubic symmetry [8]. Such a spectrum is usually characteristic of erbium in single-
crystal silicon with a low (compared to the erbium concentration) oxygen content. At the same
time, the integrated luminescence intensity of the Er
3+
ion in the structure obtained in the SPE
mode is 2 times higher than that in the structure grown in the MBE process. According to existing
ideas about the mechanism of TFE of amorphous silicon layers sawn in a vacuum onto a single-
crystal substrate, during annealing the epitaxial crystallization front moves from the single-
crystal/amorphous film interface to the surface of the layer [9].
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ResearchBib IF-2023: 11.01, ISSN: 3030-3753, Valume 1 Issue 10
Fig. 2. PL spectrum of the structure grown in the SPE mode. The PL recording conditions
are the same as for the spectrum in Fig. 1.
If at an annealing temperature of 600
◦
C the crystallization of amorphous silicon on a single-
crystal substrate occurs due to the epitaxial ordering of atoms of the amorphous phase near the
single-crystal/amorphous film interface, then at 800
◦
C there is additional nucleation and growth
of randomly oriented crystallites in the bulk of amorphous silicon. The epitaxial crystallization
rate at 80
◦
С is 2.2–10 nm/min. Such a high crystallization rate leads to the fact that at the end of
annealing part of the surface is occupied by the single-crystal phase, and the other part is occupied
by the polycrystalline phase. The effect of oxygen on the slowing down of the crystallization rate
was reported in [10]. However, when oxygen was admitted in our experiments at the moments of
suspension of the growth process, an insignificantly thick layer of adsorbed gas is probably
formed, which, perhaps, is only partially captured by the growing layer. As a result, the total
amount of oxygen introduced into the layer is insignificant. This apparently causes the observed
changes in the photoluminescence spectrum of Er
3+
ions in silicon layers grown by the SPE
method. Thus, the solid-phase epitaxy method allows one to form a heavily erbium-doped layer in
a silicon film sawn in an ultrahigh vacuum, from which more intense photoluminescence is
observed than from a layer grown by the molecular beam epitaxy method.
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