1063-7397/05/3403- © 2005 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 34, No. 3, 2005, pp. 160–172. Translated from Mikroelektronika, Vol. 34, No. 3, 2005, pp. 196–209.
Original Russian Text Copyright © 2005 by Tikhonov.
Magnetic-ﬁeld sensors integrated with electronic
circuitry and actuators have found many uses in process
control, automotive electronics, avionics, scientiﬁc
instrumentation, nondestructive testing, biomedicine,
and consumer electronics . Such microsystems are
produced in tens of billions per year worldwide.
In Russia, integrated magnetic-ﬁeld sensors are still
fabricated on quite a modest scale. The situation might
be remedied by developing innovative technologies.
The ultimate capabilities of a complete microsystem
are determined by the magnetic-ﬁeld sensor. Although
this is most commonly implemented as a Hall-effect
sensor or a magnetoresistor, bipolar magnetotransistors
(BMTs) have emerged as a potential alternative .
BMTs can offer high sensitivity, can discriminate
between different directions of applied magnetic ﬁeld,
and can be integrated with complementary metal–
oxide–semiconductor (CMOS) peripheral circuits and
with metal–oxide–semiconductor (MOS) ﬁeld-effect
power transistors on a common substrate.
BMTs have long been investigated by many workers
both in Russia and abroad, yet some issues must be
resolved before they ﬁnd widespread use. These are
collector-current imbalance, marked variation of per-
formance with external conditions, and poor sensitivity
to weak magnetic ﬁelds.
To gain a deeper understanding of how the BMT
operates, a series of computer-simulation studies was
conducted by Kozlov
[3, 4, 8, 12–18], Tikhonov
[5, 9–11], Amelichev
, and Korolev
. The research formed the background to new con-
cepts for microsystems based on high-sensitivity BMT
sensors. Furthermore, the following important points
have been made:
(i) The ﬁeld-induced differential collector voltage
changes sign as the base bias
is increased, leading
to a negative relative magnetic-ﬁeld sensitivity of col-
(ii) If the base region is realized as a diffused well,
the BMT shows threshold behavior: at zero well–sub-
strate voltage, the collector currents start growing rap-
once this has passed a speciﬁc threshold.
(iii) High-sensitivity BMTs might be created if one
makes use of the fact that the relatively low currents
through the sensing collectors are changed mainly due
to the Lorentz force acting on the relatively high emitter
The simulations have made it possible to construct
and validate a model of negative relative sensitivity that
essentially includes the formation of an electron–hole
plasma and the bulk recombination of electrons and
The new conceptions have been used to devise the
base-in-well BMT (BWBMT), a variation of the BMT
that is placed in a diffused well in order to decouple it
from other devices on the substrate [19, 20]. BWBMTs
can sense even the earth’s magnetic ﬁeld, are little
affected by the conditions on their surface, and are less
sensitive to the collector-current imbalance.
Individual BWBMTs and BWBMT-based elec-
tronic compasses were fabricated at Technological
Centre, a subsidiary of the Moscow Institute of Elec-
tronic Engineering (Technical University).
In the present study, a computer simulation of the
BWBMT is conducted in conjunction with an experi-
ment in order to facilitate integration of the device into
Response Mechanism of the Base-in-Well Bipolar
R. D. Tikhonov
Technological Centre, Moscow Institute of Electronic Engineering (Technical University), Moscow, Russia
Received November 10, 2004
—For the base-in-well bipolar magnetotransistor, a computer simulation is conducted in conjunction
with an experiment. The following points are made: (i) Bulk recombination is important in the response of the
device to an applied magnetic ﬁeld. (ii) The device shows threshold behavior. (iii) The relative magnetic-ﬁeld
sensitivity of collector current is dependent on the applied magnetic ﬂux density; moreover, the former grows
in magnitude with decreasing ﬂux density if this is sufﬁciently low. (iv) The relative sensitivity changes sign as
the base bias is varied. A maximum relative sensitivity of about 2000 T
is achieved in measurements of the
earth’s magnetic ﬁeld.
MICRO- AND NANOELECTRONIC