1063-7397/04/3306- © 2004 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 33, No. 6, 2004, pp. 373–376. Translated from Mikroelektronika, Vol. 33, No. 6, 2004, pp. 459–463.
Original Russian Text Copyright © 2004 by Dvoryankin, Dikaev, Krikunov, Kudryashov, Telegin, Babichev, Baru, Porosev, Savinov.
X-ray photovoltaic detectors made in epitaxial
GaAs technology suffer little from leakage-current
noise because they require no bias voltage and operate
at room temperature . Arrays of such detectors pro-
vided with readout circuitry are useful for digital x-ray
imaging . However, it is highly desirable that constit-
uent detectors be uniform in response and free from
cross coupling (these factors affect image quality and
array dynamic range). The former requirement implies
screening detector arrays in terms of uniformity of
This paper reports an experimental evaluation of
one-dimensional (1D) arrays of 64 GaAs x-ray detec-
tors designed for digital imaging. They were fabricated
and pretested at the Institute of Radio Engineering and
Electronics, using a Zond-A5 multichannel tester. Inte-
gration with readout circuitry and full-scale testing
were at the Budker Institute of Nuclear Physics.
The detector arrays are realized as a GaAs strip 25.6
mm long and 0.4 mm wide, coated with an encapsulant.
The constituent detectors are separated by trenches of
depth 0.1–0.12 mm arranged with a pitch of 0.4 mm.
The trench width is 10% of the detector size. The GaAs
strip is attached to an alumina-ceramics base (purity
over 99.5%) provided with 64 metallic bars of width
0.2 mm and pitch 0.4 mm, to which the detectors are
connected. The connectors are ultrasonically bonded
aluminum wires of diameter 20–50
m. The design is
illustrated by Fig. 1.
Prior to integration with readout circuitry, the arrays
were pretested with the aid of a Zond-A5 tester having
64 input pins, each of which connected a constituent
detector to a ﬁeld-effect transistor as shown in Fig. 2.
The variable resistor
of each channel is used to
adjust the channel gain so that the signals be uniform to
within 5% over the array. The respective responses of
individual detectors to x rays are sensed sequentially at
a proper rate and displayed on an oscilloscope or
recorded with a tracer.
Pulsed irradiation was employed for the detector–
ampliﬁer system to be unaffected by dark current, the
constant signal component being rejected by a capaci-
tor. The x-ray intensity varied between an almost zero
level and a maximum determined by the voltage and
The x-ray pulse rate was 50 Hz (due to half-wave
rectiﬁcation), so that the tester scanned the array in
1.28 s. As the x-ray pulses were the same to within
10%, so was the accuracy to which the magnitude of
detector response was measured. The response was 15–
A min Gy
for photon energies of 30–40 keV.
1D GaAs Detector Arrays for Digital X-ray Imaging
V. F. Dvoryankin*, Yu. M. Dikaev*, A. I. Krikunov*, A. A. Kudryashov*,
A. A. Telegin*, E. A. Babichev**, S. E. Baru**, V. V. Porosev**, and G. A. Savinov**
* Fryazino Branch, Institute of Radio Engineering and Electronics, Russian Academy of Sciences,
Fryazino, Moscow oblast, Russia
** Budker Institute of Nuclear Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
Received September 8, 2003
—1D imaging arrays of GaAs x-ray detectors are designed, fabricated, and tested. Each array consists
of 64 detectors arranged with a pitch of 0.4 mm. In x-ray testing, an almost linear relationship is found between
the detector response and the tube current. Zero detector cross coupling is observed in scanning an x-ray beam
along any array.
MICRO- AND NANOELECTRONIC DEVICES
Sketch of the GaAs detector array: (
) constituent detector, (
) alumina-ceramics base, (
) metallic bar, (
) common cathode,