1063-7397/02/3102- $27.00 © 2002 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 31, No. 2, 2002, pp. 84–87. Translated from Mikroelektronika, Vol. 31, No. 2, 2002, pp. 99–103.
Original Russian Text Copyright © 2002by Mittova, Tomina, Sukhochev, Prokin, Vasyukevich.
Previous research has revealed that using
elements and their compounds as oxidation promoters
of III–V semiconductors, such as GaAs, offers much
room to manipulate the growth mechanism and, hence,
the properties of oxide ﬁlms [1–3]. Thermal oxidation
strongly depends on whether the promoter is fed at a
limited or unlimited rate.
The present experimental study addresses solid-
phase reactions in the thermal oxidation of GaAs cov-
ered with an Ni layer.
The Ni/GaAs heterostructures were fabricated from
GaAs(100) wafers (SAGOCh-1) whose surface was
treated with a 49% hydroﬂuoric acid for ten minutes and
repeatedly rinsed in distilled water. The Ni layer was
deposited by thermal evaporation (at
using a VUP-5 exhaust unit. The original Ni purity was
98.9%. It was measured with a VRA-30 x-ray ﬂuores-
cence analyzer, which has a sensitivity of
and is accurate to within 1% or so. Ni thickness was
found to be
nm. This was determined with an
MII-4 interference microscope.
The heterostructures were oxidized in the continu-
ous quartz reactor of a horizontal-tube resistor furnace,
the process temperature controlled with a BPRT-1 unit
(accurate to within
C). Oxidation was carried out in
during 5–50 min. The oxide ﬁlms
were grown by a reoxidation technique, with which the
entire isothermic thickness–time characteristic is
obtained from a single specimen. Oxide thickness was
measured with an LEF-3M ellipsometer (accurate to
RESULTS AND DISCUSSION
The kinetics of thermal oxidation was modeled with
is the oxide thickness
is the effective rate constant (nm
is the oxidation time (min). The isothermic thickness–
time characteristics for the oxidation are shown in Fig. 1.
Kinetic data were derived according to Mittova
 and are collected in Table 1.
The fact that
< 0.5 implies that the oxidation is
governed by diffusion-limited solid-phase reactions
. Since the curves are free from kinks, we can infer
that the oxidation mechanism does not change with
time. The effective activation energy (EAE) was found
to be 317 kJ/mol, a value higher than that for the oxida-
tion of bare GaAs (110 kJ/mol). The reason is that the
respective major processes are different in character
from each other, which accords with previous ﬁndings
concerning the oxidation of Ni/InP .
The oxide ﬁlms were also examined by IR spectros-
copy, ultrasoft-x-ray emission spectroscopy, and x-ray
The IR-spectroscopy study (Fig. 2) was carried out
over the range 400–1400 cm
, using a UR-10 two-beam
spectrophotometer. It was found that the oxide ﬁlms are
mainly composed of Ga
(475 and 525 cm
)  and
NiO (560 and 825 cm
). All specimens exhibited the
Solid-Phase Reactions in the Thermal Oxidation
of Ni/GaAs Heterostructures
I. Ya. Mittova, E. V. Tomina, A. S. Sukhochev, A. N. Prokin, and A. O. Vasyukevich
Voronezh State University, Voronezh, Russia
Received October 15, 2001
—The thermal oxidation of GaAs covered with an Ni layer is studied experimentally. It is shown that
this layer makes for better dielectric performance of the oxide ﬁlm and inhibits the escape of the volatiles from
GaAs. A possible pattern of the oxidation of Ni/GaAs heterostructures is put forward. It includes the formation
of a transition layer between NiO and GaAs, which contains nickel–arsenic and nickel–gallium compounds.
Reactions at the interface between the transition layer and NiO are considered.
Kinetic data on the thermal oxidation of Ni/GaAs
EAE, kJ/mol 317