ISSN 10637397, Russian Microelectronics, 2011, Vol. 40, No. 8, pp. 543–552. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.M. Zaletin, V.P. Varvaritsa, 2010, published in Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki, 2010, No. 3, pp. 4–13.
By its nature, the semiconductor detector of
nuclear radiation places enormous demands on the
material employed. The highest purity and structural
quality can be achieved with silicon or germanium;
accordingly, these were the first to be used for the pur
pose. Indeed, they brought a dramatic change to
nuclear spectrometry, monitoring, and screening, and
continue to occupy a dominant position in the area.
On the other hand, the two materials, and silicon in
particular, are not well suited for radiation detection in
industrial or field environments. They show modest
stopping power and radiation hardness; furthermore,
detectors based on any of them require cooling (some
also do so when not operated). Efforts are therefore
being made to find alternative semiconductors that
would be suitable for wider areas of application and
would operate at room temperature. Specifically, they
should meet the following requirements [1–6]:
(1) The energy gap
should exceed 1.4 eV in order
to ensure a sufficiently low carrier density in the bulk
material at room temperature.
(2) The effective atomic number
30 in order to provide adequate absorption of X and
(3) The energy
of electron–hole pair production
should be close to the energy gap.
(4) For gammaray detectors,
is the energy of an incident photon;
is the equi
librium carrier density, cm
is the sensitive vol
ume of the detector, cm
. This means that roomtem
perature fluctuations in the total number of equilib
rium carriers should be far less in magnitude than the
total number of photogenerated carriers.
the carrier mobility and lifetime, respectively, the sub
scripts e and h standing for electrons and holes. The
inequality is designed to ensure full charge collection
and to prevent polarization.
These are stringent specifications; in fact, they
conflict with each other in some cases and are there
fore impossible to meet by any material. So we have to
be prepared to make compromises. Requirement (1)
suggests using binary or pseudobinary compounds;
otherwise, departures from stoichiometry are likely.
Table 1 lists candidate compound semiconductors
for roomtemperature detection of X or gammarays.
AlSb is probably the most tempting to try, with its large
effective atomic number (
= 13, 51), an energy gap as
wide as 1.68 eV, and carrier mobilities a few times as
high as those of other compound semiconductors. In
fact, efforts to grow AlSb crystals were made in the
Soviet Union (at the Giredmet research institute in
Moscow and the HighPurity Metal Works in Svetlo
vodsk) and elsewhere, including
. None of
them were successful due to the great affinity of alumi
num for oxygen and the high volatility of antimony.
Below, we present a brief status report on the
research into widebandgap compound semiconduc
tors for X and gammaray detectors in Russia.
WideBandgap Compound Semiconductors
for X or GammaRay Detectors
V. M. Zaletin
and V. P. Varvaritsa
Dubna International University of Nature, Society, and Man, Dubna, Moscow oblast, Russia
Analitnauchtsentr Limited Liability Company, Moscow, Russia
—Although Ge and Si are currently the major semiconductor materials for nuclearradiation detec
tors used in highresolution nuclear spectroscopy, and will remain so in the foreseeable future, their limita
tions that hamper their use in field and industrial environments have given the impetus for research into alter
native semiconductors that would be suitable for wider areas of application and would operate at room tem
perature. Requirements are formulated for semiconductors in which to make roomtemperature detectors of
X or gammarays. A brief overview is given of the work in Russia on such detectors using a widebandgap
compound semiconductor, namely, CdTe, GaAs, HgI
, or TlBr. The standard of semiconductormaterials
technology is shown to be a key factor in developing this type of detector.
gammarays, detector, crystal, semiconductor, resolution, photons, compounds, efficiency,
AND TECHNOLOGY: SEMICONDUCTORS