analytica chimica acta 615 (2008) 1–9
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/aca
Review
Novel semiconductor materials for the development of
chemical sensors and biosensors: A review
Nikos Chaniotakis
∗
, Nikoletta Sofikiti
Laboratory of Analytical Chemistry, Department of Chemistry, University of Crete,
Voutes 71003 Iraklion, Crete, Greece
article info
Article history:
Received 15 November 2007
Received in revised form
13 March 2008
Accepted 18 March 2008
Published on line 30 March 2008
Keywords:
Chemical sensor
Biosensor
Semiconductor
Gallium nitride
Indium nitride
Conductive diamond
Transduction
Surface potential
abstract
The aim of this manuscript is to provide a condensed overview of the contribution of certain
relatively new semiconductor substrates in the development of chemical and biochemical
field effect transistors. The silicon era is initially reviewed providing the background onto

the active layer, and the final size and shape of the complete
device. Most importantly, it has been known early on that the
chemical characteristics of the active area of the semicon-
ductor play a major role in determining the behavior and the
performance of the final device. This is indeed the case since
a close look at the interfacial processes involved during the
operation on transistors will reveal that it is without a doubt a
chemical process technology. Based on these facts it was clear
that the precise control of the surface chemistry was manda-
tory for the final optimization of the device performance. For
this reason there are some basic parameters that need to be
taken into account when new semiconductor materials are
to be developed and optimized, and which play a decisive
role in their applicability to biosensors. The chemical synthe-
sis (growth) of the material, the post-material treatment such
as doping or ion implantation and the final chemical surface
treatment are the three most important ones. The develop-
ment and optimization of these semiconductor technology
procedures has allowed for the growth or synthesis of materi-
als withvery well controlled and unique physical and chemical
characteristics, down to the atomic level.
The main parameter, which has been shown very early to
play a very significant role in the behavior of these mate-
rials, especially in their application to bio-FETs as well as
all other electrochemically based biosensors, is the-what-
is-called “work function”, “contact potential”, or “electrode
potential”. Even though there might be some fine differences
between these terms, for the purpose of this work we will refer
to all these terms as the “surface potential” of the semiconduc-
tor. Semiconductor surface potential plays an important role

germanium and in silicone semiconductors [7]. It was shown
in these early works that the surface chemistry of the material
is determined by the active chemical functionalities found at
the surface, and to a lesser degree by the crystal orientation. At
the same time, the type and amount of the surface chemical
functionalities depend on both the chemical composition of
the material itself, as well as, on any chemical post-treatment
of the surface.
The surface chemistry, or to be more precise the surface
chemical functionalities, can induce specific physicochemi-
cal properties of the semiconductor as presented early on by
Bardeen and Morrison [5], and proven by many other scientists
since then. Those are:
1. Work function or contact potential [8–13].
2. Rectification [14,15].
3. Chemical reactions with electron transfer [16,17].
4. Adsorption [18,19].
5. Surface recombination–photoconductivity [20,21].
6. Change in contact potential with light [22].
7. Surface conductance–channel effect [23].
8. Change in surface conductance with electrostatic
field–field effect [24–26].
9. Noise.
All these properties can be used as the basis for the
development of analytically useful devices, including chem-
ical sensors, biosensors, and bio-chem-FETs. This is due to
the fact that external chemical stimuli can drastically alter
these fundamental and easily measurable surface semicon-
ductor properties. Monitoring surface current, potential or
impedance characteristics can be directly related to the chem-

sensitivity of semiconductor-based FBARs will depend on both
the initial physical characteristics of the material, as well as
the induced physical changes upon chemical interaction of
the analyte with the sensing surface. Finally, amperometric
sensors are dependent on changes in either the conductance
of the material, or changes in the activity of redox species
available within the sensor element.
It is thus clear from the above that creating chemical
sensors or biosensors from semiconductors requires precise
chemical control of the surface chemistry. Only under these
conditions the analytical characteristics of the sensor such as
selectivity, sensitivity, detection limit, response time, and sig-
nal stability can be optimized. Since analyte recognition and
detection is a result of the perturbation of the electro optical
properties of the semiconductor surface and subsurface layers
there must be a specific and reversible chemical interaction
of the analyte with the semiconductor sensing element. As
the material science community evolved and was able to have
complete control of the growth process, more and more these
materials were used for the development of sensors.
2. The silicon era
In the late 1960s, the use of silicon as a matrix for integrated
sensor–transducer systems had begun [28,29]. Silicon-based
devices for the in vivo measurement of electrophysiological
measurements had already been developed. The revolution
came from a publication of Bregveld [23], in which he showed
that Si-based devices, the so-call pH-FETs, can be used to mea-
sure pH in very small volumes, and with good accuracy. This Si
technology came to maturation with the commercialization of
these pH sensors in the mid-80’s, while they were the platform

signal to noise ratios, thus allowing for the development of
large sensor arrays highly useful in the area of biochips.
One of the major obstacles to overcome during the design
of a continuous sensing system is the long-term storage and
operational stability of the sensing element. Even though SiO
2
and its related metal tin oxide substrates are very selective
substrates for the detection of hydrogen ions, their stability
in harsh environments is limited. Treatment with very acidic
or basic solution, or fluoride containing solutions should thus
be avoided since it can be detrimental to the analytical behav-
ior of these systems. Surface etching and oxidation in these
solutions will result in the drastic decrease in the sensitivity,
while the response time increases considerably. In addition
the proper isolation between the devices and the chemical
solutions, as well as the sensitivity to light are still issues to
be completely resolved. It is therefore a challenge to develop
inert semiconductor electrodes.
The bio-chemical sensors developed up until very recently
were based on the pH sensitive FETs. Any chemical or bio-
logical process that can result in changes of the pH can be
combined with a pH-FET transducer, resulting in what is called
CHEMFET of BIOFET. In all of these devices, the surface poten-
tial developed at the surface of the semiconductor is based on
the direct interaction of the ligand with the exposed atoms
of the semiconductor, as shown in Fig. 5 [30]. This chemical
interaction (chemisorption or coordination) of the charged or
polarized analytes with the semiconductor surface induces
a surface potential. It is important to recognize this fact,
which is much more pronounced and important for the design

withstand larger voltages, they have higher thermal conduc-
tivity, and they are more stable over time and thus are more
reliable. Moreover, the aforementioned WBG materials have
excellent reverse recovery characteristics, and for this reason
they require less time and energy to return to the base line
signal. In addition they are less susceptible to electromag-
analytica chimica acta 615 (2008) 1–9 5
Table 1 – Summary of the analytical applications of
novel semiconductor materials
Gas sensing (H
2
,NH
3
,NOx,O
2
,
CO, H
2
O, combustion gases,
ethanol, organic vapours,
hydrocarbons, fluorocarbons)
GaN [33–42]
InN [43]
AlN [44–46]
SiC [47–53]
Ion sensing
GaN [54–60]
InN [61]
Diamond [62,63]
Other electroanalytical applications Diamond [64–74]

3
-hybridization of carbon atoms in dia-
mond and the steric hindrance of such surfaces, are the main
reasons for the chemical inertness of diamond.
Despite that, there are several notable exceptions to the
generally low reactivity of diamond. First of all diamond sur-
faces can be oxidized by several post-growth treatments, such
as oxygen-ambient annealing [94], oxygen-plasma treatment
[93] or anodic polarization [95]. All these oxidizing techniques
result in an increase of surface O/C ratio and the presence of
carbon–oxygen bonds. An important characteristic of this sur-
face is that this oxygen termination can partially regenerated
by subsequent acid washing and hydrogen-plasma treatment
[93].
Another very useful modification of diamond surface is
the halogenation using atomic and molecular chlorine and
fluorine [96,97]. Although molecular Cl
2
and F
2
have been
used as reagents, the reaction conditions are such that atomic
radical species are produced. Since the reaction conditions
required are very extreme (for example, Cl
2
/400–500
◦
C), and
thus unsuitable for large-scale implementation, the photo-
chemical radical production is usually preferred [98].

surface is insignificant, leading to improved resistance to sur-
face deactivation and fouling. It should be mentioned though
that the surface chemistry of the diamond is strongly influ-
enced by the amount of boron doping [103,104].
All the above-mentioned properties, along with the fact
that diamond is considered highly biocompatible, make this
material ideal for the development of completely integrated
bioelectronic sensing systems. This seems to be true since
already a large number of diamond’s electroanalytical appli-
cations have been reported, in flow-injection analysis (FIA)
systems or ion and high-performance liquid chromatogra-
phy (IC & HPLC), for the detection of azide [63,64], metal
ions [63,65], nitrite [63], dopamine [63,66,67], chlorpromazine
[63], hydrazine, biogenic aliphatic polyamines [68,69], NADH
[70], uric acid [71], histamine and serotonin [72], and carba-
mate pesticides [73]. It is worth to be mentioned that, in all
the above cases, diamond demonstrated superior electrode
performance in terms of linear dynamic range, sensitivity,
limit of detection, response stability and long-term activity,
as compared with glassy carbon. In the field of electrocataly-
sis some interesting applications have also been reported, for
the oxidation of methanol and the reduction of oxygen, both
using a conductive, dimensionally stable diamond electrode
containing Pt nanoparticles [80–82]. Another very attractive
application of diamond, coming from the area of spectro-
electrochemistry, was reported in 2001 [105], concerning a
free-standing boron-doped diamond disc (0.38mm thick and
8 mm in diameter) used for the oxidation of ferrocyanide, or
the reduction of methyl viologen, and the simultaneous spec-
troscopic monitoring of the products through the disc. In the

entation is the fact that the outer most atomic layer has three
bonds to the underlying nitrogen atomic plane while the forth
unoccupied bond (tangling bond) is available for interaction
with ligands that exist within the close proximity test envi-
ronment. The type of ligands that can interact chemically with
this surface will thus depend on the chemistry of the surface
layer of the material. Extensive studies [107] have proven that
there is an induce polarity in these bonds, with the more elec-
tropositive atoms being electron deficient relative to nitrogen
atoms, as shown in the case of GaN in Fig. 4 [108].
Up until very recently, the growth of these materials was
not very well controlled, and thus their availability for sen-
sor applications was very limited. Of these, the polar GaN
c-plane is the first of the III-nitrides to be available at high
crystal quality and because of this it has been more exten-
sively studied for sensor applications. In particular, of the two
possible orientations of the c-plane GaN, the Ga-face is the
one almost exclusively used. This is due to the fact that this
material is very robust, inert to etching, while at the same
time it has available free bonding for coordination with Lewis
base-type ligands. In addition it can be chemically function-
alized, thus allowing the possibility to generate multi-layer
chemical systems [78]. On the other hand the N-face struc-
ture is not chemically stable; it etches easily, while at the same
time it cannot coordinate with bases due to the unfavorable
electronic charge density distribution.
Since most of the published work is based on the c-plane
GaN Ga-face, we will concentrate on this particular substrate
for the remaining of this section. Based on theoretical results
the outer most layer of the GaN, and in particular the Gal-

It should be pointed out that the exact nature of the sur-
face chemistry of GaN is very important since any changes
will drastically influence the behavior of the final device. For
example, it is known that oxidation of the surface will gen-
erate a surface layer saturated with hydroxyl groups. In this
case, the behavior of the sensor will be reversed, since it will
now be sensitive to cations, and not to anions as in its origi-
nal state. Additionally, care must be taken so that the studies
used for the evaluation of these sensors do not involve any
pH changes, since this can interfere with the measurement
of the analyte ions. These studies of the GaN surface indicate
that the unique selectivity of the GaN surface is very impor-
tant for the future development of not only electrochemical
sensors and biosensors, but also optical fluorescent sensors.
Indium nitride (InN) is a semiconductor for which there
has been done very little work in the area of chemical sen-
Fig. 6 – Correlation between the activity of KCl and the
induced potential and interfacial capacitance of the Ga-face
GaN-solution interface. Reproduced with permission from
Ref. [59].
Fig. 7 – IDS–VDS characteristics of a GaN EGHEMT with
Lg=80␮m and Wg= 100 ␮m, measured in air (— black solid
line) and within aqueous solutions with pH 3.35 (··· red
dotted line), pH 6.84 (–·– blue dashed-dotted line) and pH
12.45 (– – magenta dashed line). Reproduced with
permission from Ref. [109]. (For interpretation of the
references to color in this figure legend, the reader is
referred to the web version of the article.)
sors and biosensors. InN is a chemically stable wurtzite crystal
which, as in the case of GaN, also has an induced polar surface.

major problem of material availability and suitability for elec-
trochemical and optical transduction is being undertaken via
multidisciplinary research efforts.
In the near future it is expected that the nano-
semiconductor structures [113–117] will have a profound
effect on the capabilities of direct bio-chemical analysis. Not
only the quantum dots and quantum planar structures will
be a major player in this area, but it is also expected that
nanoporous and especially nanorods and nanocolumn arrays
will provide new directions for the development of chemi-
cal sensors and biosensors capable in tackling the modern
challenges of direct chemical analysis. These semiconduc-
tor materials will allow for the simultaneous emission and
detection of the signal, while it is envisioned that reagent-
less multi-parameter analysis will be achievable. For this,
coordinated research efforts embracing both synthetic and
analytical groups will facilitate the design and the materializa-
tion of these novel semiconductor-based analytical devices.
references
[1] J. Bardeen, W.H. Brattain, Phys. Rev. 74 (1948) 230.
[2] K.S. Cole, J. Appl. Phys. 3 (1932) 114.
[3] S.R. Morrison, The Chemical Physics of Surfaces, 2nd ed.,
Plenum Press, New York, London, 1977, pp. 263–300.
[4] W.H. Brattain, C.G.B. Garrett, Physica 20 (1954) 885.
[5] J. Bardeen, S.R. Morrison, Physica 20 (1954) 873.
[6] P.J. Boddy, J. Electroanal. Chem. 10 (1965) 199.
[7] R.M. Hurd, P T. Wrotenbery, N. Y. Ann., Acad. Sci. 101 (1964)
576.
[8] G.C. Dousmanis, Phys. Rev. 112 (1958) 369.
[9] J. Mizsei, J. Hars

[24] J.E. Thomas, R.H. Rediker, Phys. Rev. 101 (1956) 984.
[25] G.F. Blackburn, Chemically sensitive field effect transistors,
in: A.P.F. Turner, I. Karube, G.S. Wilson (Eds.), Biosensors:
Fundamentals and Applications, Oxford Science
Publications, 1987, pp. 481–
530.
[26] S. Shiono, Y. Hanazato, M. Nakako, Bioanal. Appl. Enzym.
36 (1992) 151.
[27] R.P. Buck, D.E. Hackleman, Anal. Chem. 49 (14) (1977)
2315.
[28] A.R. Zias, C.W. Clapp, D.J. DeMichele, P.R. Emtage, D.K.
Hartman, J.W. Savery, R.C. Thomas, Exp. Mech. 3 (1963) 19A.
[29] K.D. Wise, J.B. Angell, A. Starr, IEEE Trans. Bio-Med. Eng. 17
(1970) 238.
[30] M. Bruening, E. Moons, D. Cahen, A. Shanzer, J. Phys. Chem.
99 (1995) 8368.
[31] B. Ozpineci, L.M. Tolbert, Comparison of Wide-Bandgap
Semiconductors for Power Electronics Applications, Oak
Ridge National Laboratory, ORNL/TM-2003/257.
[32] J. Grant, W. Cunningham, A. Blue, V. O’Shea, J. Vaitkus, E.
Gaubas, M. Rahman, Nucl. Instrum. Meth. A 546 (2005) 213.
[33] X.H. Wang, X.L. Wang, C. Feng, C.B. Yang, B.Z. Wang, J.X.
Ran, H.L. Xiao, C.M. Wang, J.X. Wang, Microelectron. J. 39
(2008) 20.
[34] M. Ali, V. Cimalla, V. Lebedev, H. Romanus, V. Tilak, D.
Merfeld, P. Sandvik, O. Ambacher, Sens. Actuators B: Chem.
113 (2006) 797.
[35] F. Yun, S. Chevtchenko, Y T. Moon, H. Morko, J.T. Fawcett,
T.J. Wolan, Appl. Phys. Lett. 87 (2005) 1.
[36] J. Kim, B.P. Gila, G.Y. Chung, C.R. Abernathy, S.J. Pearton, F.

[49] E.J. Connolly, B. Timmer, H.T.M. Pham, J. Groeneweg, P.M.
Sarro, W. Olthuis, P.J. French, Sens. Actuators B: Chem. 109
(2005) 44.
[50] E.J. Connolly, H.T.M. Pham, J. Groeneweg, P.M. Sarro, P.J.
French, Sens. Actuators B: Chem. 100 (2004) 216.
[51] S.A. Khan, E.A. De Vasconcelos, H. Uchida, T. Katsube, Sens.
Actuators B: Chem. 92 (2003) 181.
[52] F. Solzbacher, C. Imawan, H. Steffes, E. Obermeier, M.
Eickhoff, Sens. Actuators B: Chem. 78 (2001) 216.
[53] W. Moritz, V. Fillipov, A. Vasiliev, A. Terentjev, Sens.
Actuators B: Chem. 58 (1999) 486.
[54] H T. Wang, B.S. Kang, T.F. Chancellor, T.P. Lele, Y. Tseng, F.
Ren, S.J. Pearton, W.J. Johnson, P. Rajagopal, J.C. Roberts, E.L.
Piner, K.J. Linthicum, Appl. Phys. Lett. 91 (2007) 042114.
analytica chimica acta 615 (2008) 1–9 9
[55] Y. Alifragis, A. Volosirakis, N.A. Chaniotakis, G.
Konstantinidis, A. Adikimenakis, A. Georgakilas, Biosens.
Bioelectron. 22 (2007) 2796.
[56] Y. Alifragis, A. Volosirakis, N.A. Chaniotakis, G.
Konstantinidis, E. Iliopoulos, A. Georgakilas, Phys. Status
Solidi A: Appl. Mater. Sci. 204 (2007) 2059.
[57] T. Kokawa, T. Sato, H. Hasegawa, T. Hashizume, J. Vac. Sci.
Technol. B 24 (2006) 1972.
[58] B.S. Kang, F. Ren, M.C. Kang, C. Lofton, W. Tan, S.J. Pearton,
A. Dabiran, A. Osinsky, P.P. Chow, Appl. Phys. Lett. 86 (2005)
1.
[59] N.A. Chaniotakis, Y. Alifragis, A. Georgakilas, G.
Konstantinidis, Appl. Phys. Lett. 86 (2005) 1.
[60] N.A. Chaniotakis, Y. Alifragis, G. Konstantinidis, A.
Georgakilas, Anal. Chem. 76 (2004) 5552.

[76] W. Yang, J.E. Butler, J.N. Russell Jr., R.J. Hamers, Langmuir 20
(2004) 6778.
[77] J. Park, Y. Show, V. Quaiserova, J.J. Galligan, G.D. Fink, G.M.
Swain, J. Electroanal. Chem. 583 (2005) 56.
[78] M. Stutzmann, G. Steinhoff, M. Eickhoff, O. Ambacher, C.E.
Nebel, J. Schalwig, R. Neuberger, G. M
¨
uller, Diamond Relat.
Mater. 11 (2002) 886.
[79] H. Kim, P.E. Colavita, K.M. Metz, B.M. Nichols, B. Sun, J.
Uhlrich, X. Wang, T.F. Kuech, R.J. Hamers, Langmuir 22
(2006) 8121.
[80] M.W. Shinwari, M.J. Deen, D. Landheer, Microelectron.
Reliab. 47 (2007) 2025.
[81] J. Wang, G.M. Swain, T. Tachibana, K. Kobashi, Electrochem.
Solid State Lett. 3 (2000) 286.
[82] J. Wang, G.M. Swain, Electrochem. Solid State Lett. 5 (2002)
E4.
[83] J. Wang, G.M. Swain, J. Electrochem. Soc. 150 (2003) E24.
[84] G. Wingqvist, J. Bjurstr
¨
om, A C. Hellgren, I. Katardjiev,
Sens. Actuators B: Chem. 127 (2007) 248.
[85] H. Noma, E. Ushijima, Y. Ooishi, M. Akiyama, N. Miyoshi, K.
Kishi, T. Tabaru, I. Ohshima, A. Kakami, T. Kamohara, Adv.
Mater. Res. 13–14 (2006) 111.
[86] A. Choujaa, N. Tirole, C. Bonjour, G. Martin, D. Hauden, P.
Blind, A. Cachard, C. Pommier, Sens. Actuators B: Chem. 46
(1995) 179.
[87] J. Bjurstrom, G. Wingqvist, I. Katardjiev, IEEE Ultrason.

10 (2001) 667.
[104] A. Denisenko, G. Jamornmarn, H. El-Hajj, E. Kohn, Diamond
Relat. Mater. 16 (2007) 905.
[105] J.K. Zak, J.E. Butler, G.M. Swain, Anal. Chem. 73 (2001) 908.
[106] H. Kawarada, Y. Araki, T. Sakai, T. Ogawa, H. Umezawa,
Phys. Status Solidi A 185 (2001) 79.
[107] A. Costales, A.K. Kandalam, M. Pendas, M.A. Blanco, J.M.
Reico, R. Pandey, J. Phys. Chem. B 104 (2004) 4368.
[108] V.G. Deibuk, A.V. Voznyi, M.M. Sletov, Semiconductors 34
(2000) 35.
[109] V.M. Bermudez, Langmuir 19 (2003) 6813.
[110] Y. Alifragis, A. Georgakilas, G. Konstantinidis, E. Iliopoulos,
A. Kostopoulos, N.A. Chaniotakis, Appl. Phys. Lett. 87 (2005)
253507.
[111] H. Lu, W.J. Schaff, L.F. Eastman, Appl. Phys. Lett. 82 (2003)
1736.
[112] O. Ambacher, J. Phys. D 31 (1998) 2653.
[113] E. Calleja, M.A. S
´
anchez-Garc
´
ıa, F.J. S
´
anchez, F. Calle, F.B.
Naranjo, E. Mu
˜
noz, Phys. Rev. B 62 (2001) 16826.
[114] L.X. Zhao, G.W. Meng, X.S. Peng, X.Y. Zhang, L.D. Zhang, J.
Cryst. Growth 235 (2002) 124.
[115] R. Calarco, M. Marso, T. Richter, A.I. Aykanat, R. Meijers, A.