ISSN 10637826, Semiconductors, 2014, Vol. 48, No. 3, pp. 307–311. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © M.S. Aksenov, N.A. Valisheva, T.A. Levtsova, O.E. Tereshchenko, 2014, published in Fizika i Tekhnika Poluprovodnikov, 2014, Vol. 48, No. 3, pp. 322–326.
307
1. INTRODUCTION
For metal–insulator–semiconductor (MIS) struc
tures on III–V semiconductor compounds, in particu
lar, on InAs, a high surface state density (N
ss
) is inher
ent in the band gap [1], the lowest value of which
amounts to (2–5) × 10
11
eV
–1
cm
–2
. In addition, for
the MIS structures on InAs, irrespective of the meth
ods of the semiconductor surface preparation and the
formation of the dielectric, hysteresis of the voltage–
capacitance (C–V) characteristics of the injection type
and a shift of the C–V curves to the negative voltage
region (the presence of a positive fixed charge) is typi
cal. It is established that this fact is related to the pres
ence of an intrinsic oxide layer of complex composi
tion on the semiconductor surface in which a large
number of charge traps is formed [1, 2]. Therefore,
contrary to the SiO
2
/Si interface, the SiO
2
/InAs and
anodelayer/InAs interfaces are characterized by a
high N
ss
value and satisfy no requirements of low N
ss
necessary for the fabrication of devices.
A decrease in the N
ss
is achieved by various ways
of interface formation. In recent years, a N
ss
of
~10
11
eV
–1
cm
–2
was obtained on In
0.53
Ga
0.47
As by
the atomiclayer deposition of Al
2
O
3
and the subse
quent annealing in hydrogen [3]. N
ss
from 5 × 10
11
to 2 × 10
12
eV
–1
cm
–2
in the band gap of an
In
0.2
Ga
0.8
As/GaAs heterostructure are achieved upon
the formation of an interface with Al
2
O
3
and Gd
2
O
3
by
the method of molecular beam epitaxy [4].
In [5–7], it was shown that, when forming MIS
structures on InAs with an anodic oxide dielectric
layer of 100 nm thick (MOS structures) grown in flu
orinated electrolytes, a decrease in the N
ss
to
~10
11
eV
–1
cm
–2
is observed.
Using InAssurface passivation with a thin (15 nm)
fluorinated anode layer (FAL), we developed tech
niques for manufacturing In
2
O
3
–SiO
2
–InAs(111)A
MIS structures with an N
ss
of <5 × 10
10
eV
–1
cm
–2
, which
provided the fabrication of multielement IRradia
tion detectors [1, 8]. The MIS structures with a FAL
have an N
ss
two orders of magnitude lower and a fixed
charge value (Q
fix
) one order of magnitude lower
(~10
11
cm
–2
) than those for structures with an anode
layer (AL) grown in fluorinefree electrolytes (N
ss
≈
10
12
eV
–1
cm
–2
and Q
fix
≈ 10
12
cm
–2
) [9]. It was estab
lished that the electrical parameters of In
2
O
3
–SiO
2
–
FAL–InAs(111)A MIS structures depend on the
amount of fluorine ions (NH
4
F) in the electrolyte and
its acidity. Studying the chemical composition of lay
ers by the method of Xray photoelectron spectros
copy (XPS) showed that the oxidation of
InAs (111)A in acid electrolyte with a high NH
4
F
concentration results in the formation of an oxy
genfree InF
x
/InAs(111)A interface, whereas the
(In
2
O
3
, As
2
O
3
)/InAs interface is formed [10, 11] as a
result of anodizing InAs in this fluorinefree electro
lyte. The radical change in the composition of fluori
nated layers enables us to establish the effect of fluo
rine on the electronic properties of the FAL/InAs
interface. With this aim, we investigate the electrical
properties of MOS structures based on InAs(111)A
with anode dielectric layers 7–20 nm thick grown in
Effect of Fluorine on the Electrical Properties
of Anodic Oxide/InAs(111)A Interface
M. S. Aksenov
a
^, N. A. Valisheva
a
, T. A. Levtsova
a
, and O. E. Tereshchenko
a, b
a
Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
^email: m.se.aksenov@gmail.com
b
Novosibirsk State University, Novosibirsk, 630090 Russia
Submitted June 11, 2013; accepted for publication June 19, 2013
Abstract—The electrical properties of metal–insulator–semiconductor structures based on InAs(111)A with
thin anodic insulator layers of various thicknesses (7–20 nm) are investigated. It is established that the oxida
tion of InAs in a fluorinated acid electrolyte results in decreasing density of surface states and fixed charge in
the anodic layer to values of < 2 × 10
10
cm
–2
eV
–1
and ~3 × 10
11
cm
–2
, respectively. Comparison of the elec
trical parameters with the chemical composition of the layers shows that an improvement in the parameters
of the fluorinated anodic oxide/InAs(111)A interface is caused by the substitution of oxygen atoms for fluo
rine in the anode layers with the formation of indium and arsenic oxifluorides and In–F bonds on the InAs
surface.
DOI: 10.1134/S1063782614030026
SURFACES, INTERFACES,
AND THIN FILMS