Markevich, V. P.

Murin, L. I.

Peaker, A. R.

English

Электронная библиотека БГУ

 
5-ая Международная научная конференция «Материалы и структуры современной 
электроники», 10–11 октября 2012 г., Минск, Беларусь 
 
 
 
INTERSTITIAL  BORON-INTERSTITIAL  OXYGEN  COMPLEX  IN  SILICON: 
 LOCAL  VIBRATIONAL  MODE  CHARACTERIZATION 
 
L. I. Murin1, V. P. Markevich2, A. R. Peaker2 
___________________________________________________________________________________________ 
1Scientific-Practical Materials Research Center of NAS of Belarus, Minsk 220072, Belarus 
2The University of Manchester, Manchester M13 9PL, United Kingdom 
E-mail: murin@ifttp.bas-net.by 
 
INTRODUCTION 
The interstitial boron–interstitial oxygen complex (BiOi) is one of the dominant radia-
tion-induced defects in oxygen-rich p-type Si crystals irradiated with MeV electrons at 
room temperature [1]. It is formed as a result of an interaction of mobile Bi atoms (gener-
ated via the Watkins replacement mechanism) with interstitial oxygen atoms. The BiOi de-
fect appears to be a very efficient compensating center in irradiated p-Si and can affect the 
parameters of devices significantly since it removes a shallow acceptor (Bs) and introduces 
a deep donor level at about EC - 0.25 eV. However, in spite of its technological importance 
the electronic properties of the BiOi center have not been understood properly, local vibra-
tional modes (LVMs) of the defect have not been identified, and there is no consensus on 
its atomic structure. According to previous theoretical modeling studies [2] the BiOi com-
plex can exist in several configurations with slightly different total energies. The electronic 
properties of the defect in these configurations are similar, but the LVMs appear to be dif-
ferent. An experimental observation of the BiOi-related LVMs may provide a solid basis 
for an unambiguous identification of the center. 
EXPERIMENTAL  DETAILS 
The samples used in the study were prepared from boron doped p-type Cz-Si crystals  
(ρ = 0.3-1 Ω·cm). For a comparison a few samples from n-type Cz-Si crystals were studied 
as well. The concentration of interstitial oxygen was determined from measurements of 
absorption band at 1107 cm-1 using the calibration coefficient 3.14×1017 cm-2 and was in 
the range (0.9-1.15)×1018 cm-3 in both n- and p-Si. 
Irradiations with 10 MeV and 6.0 MeV electrons were performed at room temperature 
with fluencies in the range 1⋅1016-5⋅1017 cm-2. Isochronal annealing was carried out in the 
temperature range 75-200 °C with 25 °C increments for 30 min at each temperature. 
IR absorption analysis was carried out using a Bruker IFS 113v spectrometer. A spec-
tral resolution of 0.5 or 1.0 cm-1 was used and the samples were measured at about 20 K 
(low temperature - LT), and at room temperature (RT). 
 110
 
5-ая Международная научная конференция «Материалы и структуры современной 
электроники», 10–11 октября 2012 г., Минск, Беларусь 
 
RESULTS  AND  DISCUSSION 
Figure 1 shows fragments of absorption spectra in the range 525-1100 cm-1 measured at 
20 K for p- and n-type Cz-Si samples irradiated with 10 MeV electrons for a dose 
3×1017 cm-2 at RT. For the n-type Si all the observed radiation-induced LVM lines (spec-
trum 2) have been detected and identified previously. The main absorption band at 836 cm-
1 is related to the well known vacancy-oxygen defect (A-center). The minor bands located 
in the region of 865-1040 cm-1 are associated with the interstitial type defects involving the 
Si self-interstitial (I), interstitial carbon (Ci), and oxygen atoms [3, 4]. In particular, the 
well known band at 865 cm-1 is related to CiOi complex, pairs of bands at 917, 1034 cm-1 
and 922, 1037 cm-1 are associated with the IO2i and I2O2i defects. The band at 936 cm-1 has 
been assigned to an I2Oi defect, while a pair of the bands at 939 and 1024 cm 1 – to an ICiOi 
complex. The bands at 991 and 998 cm-1 are related to I3CiOi and I2CiOi defects, respec-
tively. The band at 648 cm-1 is a combination mode arising from the single interstitial oxy-
gen atoms. 
Only very weak traces of the bands related to complexes involving the Si self-interstitial 
and/or Ci atoms can be detected in the spectrum of irradiated p-type Si. This observation 
indicates that there are some other traps, which are more efficient in capturing mobile ra-
diation-induced I atoms than oxygen- and carbon-related centers, in this material and the 
appearance of some new complexes is expected. These complexes can give rise to vibra-
tional absorption bands. Actually, as one can see in Fig. 1 (spectrum 1) in irradiated p-Si a 
new set of radiation-induced absorption lines is appearing. The most intense of them are 
positioned at about 538, 551, 688, 721, 756 and 991 cm-1 (the later band cannot be related 
to the I3CiOi defect since the other bands related to InCiOi are absent). All the bands are 
clearly observed also in the absorption spectrum measured at RT (Fig. 2). At room tem-
perature the band positions are shifted to lower frequencies by about 3-5 cm-1 and such 
shifts are typical for the LVMs due to radiation induced defects in silicon. 
600 700 800 900 1000 1100
0.0
0.2
0.4
0.6
0.8
18Oi
756
10B+O
i
11B
647
622
551
538 688
836
721 O2i
 
991
VO
A
bs
or
pt
io
n 
co
ef
fic
ie
nt
, c
m
-1
Wavenumber, cm-1
1
2
 
600 700 800 900 1000
0.0
0.1
0.2
0.3
0.4
0.5
Ab
so
rp
tio
n 
co
ffi
ci
en
t, 
cm
-1
irrad
125 C
150 C
175 C
200 C
Wavenumber, cm-1
987718686
546534 ? 10B
11B
 
Fig. 1. Fragments of absorption spectra measured 
at 20 K for Cz-Si samples irradiated with 
10 MeV electrons for a dose 3×1017 cm-2. 
1 – p-Si ([Oi] = 1.0×1018, [Cs] ≤ 5×1015,  
[Bs] = 8×1016 cm-3); 2 – n-Si ([Oi] = 1.15×1018, 
[Cs] = 5×1015, [P] = 6×1014 cm-3) 
Fig. 2. Fragments of absorption spectrum meas-
ured at RT for p-Cz-Si sample irradiated with 
10 MeV electrons for a dose 3×1017 cm-2 and 
then subjected to isochronal anneals with the last 
steps at the temperatures indicated above the 
curves 
 111
 
5-ая Международная научная конференция «Материалы и структуры современной 
электроники», 10–11 октября 2012 г., Минск, Беларусь 
 
It should be mentioned that the same set of the LVM bands was detected also in the ir-
radiated samples with a lower boron content (ρ = 0.5-1 Ω·cm), but the intensities of the 
bands in these samples were lower than those in the samples with ρ = 0.3 Ω·cm. This find-
ing suggests an involvement of boron atoms in the composition of the center responsible 
for the bands. According to earlier studies, irradiation of Si samples with low oxygen and 
high boron content did not result in an appearance of the boron-related bands mentioned 
above and observed by us in the oxygen rich samples. The later fact indicates the presence 
of oxygen atoms in the center giving rise to a new set of the LVM bands. It seems reason-
able to suggest that this center is a BB
 
 
 
mentioned that a strong absorption by free holes and the presence of intense 
pea
FTIR spectroscopy was used to  oxygen-related defects in Cz-
gro
C-009) is thanked for a financial support. 
iOi defect. Such an assignment is supported by the re-
sults of the thermal stability study of the 
bands observed. 
Figure 3 shows the development of the 
IR absorption spectra measured at low 
temperature for an irradiated p-Cz-Si sam-
ple after 30-minutes isochronal annealing 
steps in the temperature range 100-200 °C. 
Upon annealing up to 150 °C there are no 
essential changes in the spectra. However, 
after annealing at 175 °C the situation 
changes drastically. All the new lines are 
not observed any more, a strong increase in 
the absorption by free holes does occur and 
a number of new rather strong peaks and 
dips are appearing. The peaks positioned at
about 668, 693 and 702 cm-1 are related to 
transitions of holes from the boron ground
1s state in the forbidden gap to the excited 
2p', 3p' and 4p' states associated with the
split-off p  1/2 valence band. A set of profound dips positioned at 521, 703, 765, 782 and 798 
cm-1 are due to resonant interaction of optical phonons with acceptor continuum states [5]. 
It should be 
ks and dips related to electronic transitions do not allow to make a definite conclusion 
that all the new relatively weak LVM lines disappear simultaneously upon annealing at 
175 ºC. However, an analysis of the spectra measured at RT (see Fig. 2) shows that such 
disappearance actually does occur. Thus, the thermal stability of the defect giving rise to a 
set of new LVM lines and a partial recovery of the free hole concentration observed upon 
its annihilation are consistent with the similar features known for the BiOi defect [1, 2]. 
CONCLUSION 
study the boron- and
wn p-type Si samples irradiated with fast electrons at RT. A set of new LVM lines with 
the same formation and elimination behaviors has been observed. The most intense lines of 
the set are found to be at 991, 721 and 550 cm-1. On the basis of an analysis of changes in 
intensity of the lines with content of impurities and annealing temperature the lines have 
been assigned to the LVMs of the BiOi defect. 
Fund for Fundamental Research (grant F12M
Fig. 3. Development of the IR absorp-
tion spectra measured at 20 K for the 
p-Cz-Si sample used in Fig. 1 after iso-
chronal annealing steps in the tempera-
ture range 100-200 °C 
500 600 700 800 900 1000 1100
0
1
2
3
4
5
6
7
200 C
175 C
150 C
100 C
125 C
as-irr
 
VO
Ab
so
rp
tio
n 
co
ef
fic
ie
nt
, c
m
-1
Wavenumber, cm-1
 112
 
5-ая Международная научная конференция «Материалы и структуры современной 
электроники», 10–11 октября 2012 г., Минск, Беларусь 
 
REFERENCES 
1. Khan, A. Role of the impurities in production rates of radiation-induced defects in silicon mate-
rials and solar cells / A. Khan [et al.] // J. Appl. Phys. 2001. Vol. 90. № 3. P. 1170. 
2. Carvalho, A. First-principles investigation of a bistable boron-oxygen interstitial pair in Si / 
A. Carvalho [et al.] // Phys. Rev. B. 2006. Vol. 73. № 24. - P. 24521036. 
 
 
 
 113


INTERSTITIAL BORON-INTERSTITIAL OXYGEN COMPLEX IN SILICON: LOCAL VIBRATIONAL MODE ARACTERIZATION

http://elib.bsu.by/bitstream/123456789/38147/1/L.I.Murin.pdf

INTERSTITIAL BORON-INTERSTITIAL OXYGEN COMPLEX IN SILICON: LOCAL VIBRATIONAL MODE ARACTERIZATION

Abstract

Similar works

Full text

Available Versions

Электронная библиотека БГУ