Transcript Hybrid Hall Effect device on Si

Gated Hybrid Hall Effect (HHE)
devices on silicon
Pratyush Das Kanungo, Alexandra Imre, Wu Bin, Alexei Orlov, Greg Snider, Wolfgang Porod
Dept of Electrical Engineering, University of Notre Dame
Nicholas.P.Carter
Dept of Electrical and Computer Engineering, University of Illinois at Urbana Champaign
Gated HHE Device – Structure and Physics
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Si MOSFET on Si Hall bar
25nm thick gate oxide,20micron gate length
20x12micron sized, 150nm thick ferromagnet on
top of gate
Hall effect on the 2DEG of inversion channel by
the fringing field of ferromagnet
Hall voltage read by passing current through the
semiconductor
Hall voltage/resistance changes with the
direction of magnetization of the ferromagnet
Binary magnetization states converted into
bistable voltage
Change of Hall voltage/resistance modulated by
gate bias – effective way of controlling power
dissipation
Vg
VH-
e- e-
I
M
VH+
Fringing field
Ferromagnet
Gate
2DEG
Si
Vg
Change in magnetization
direction (M) => Change in
sign of Hall voltage (VH+
I
to VH-)
Change in gate voltage (Vg)
=> Change in magnitude of
Hall voltage
VH+
M
e- e-
VH-
HHE device – magnetoelectronic system
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Information written as
magnetization states by passing
a write current through a current
line
 HIGH, and LOW output Hall
voltage according to direction of
magntization.
 Good remanance in the
ferromagnet may lead to
hysteresis loop and hence
memory
 Easily integrated with rest of the
CMOS circuit
Device structure
HHE integrated with CMOS logic
HHE device-interfacing MQCA
MQCA Array
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Magnetic Quantum Cellular
Automata (MQCA) cells can
store information
Different magnetic logics can be
performed
Can be fabricated on Si
substrate at room temperature
HHE device can interface
MQCA with CMOS using the
same principle of Hall effect
Information can be stored, and
processed magnetically, and will
be read electrically
Spin direction equivalent to
logic “0”
Spin direction equivalent to
logic “1”
Proposed device-MQCA interfaced with HHE devie
Fabrication of HHE device-I
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Hall Bar defined in thick (240nm) field oxide by image reversal and
mesa etch.
Field oxide
P type Si
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Metal (Ti/W) gate defined on top of Hall Bar, and n-wells formed
through ion implantation
Gate metal
n well
Gate oxide
n well
Fabrication of HHE device-II
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Gold bonding pads formed by image reversal and lift-off
Metal bond pad
n well
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n well
Supermalloy deposited on top of the gate by e-beam lithography
Supermalloy
n well
n well
Fabricated HHE device, and MQCA at Notre Dame
drain
Magnetic dot
Thirty three antiferromagnetically coupled magnetic dots – MQCA chain
I
gate
drain
source
4μ
12μ
10μ
HHE device
Magnet
Magnetic domains in the ferromagnet
Bistable Hall voltage and gate bias modulation
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Drop/increase of Hall voltage from HIGH to LOW modulated by gate bias
 More gate bias, less Hall voltage/voltage drop/increase, and vice versa
HIGH
B (external)
B (external)
VH
VH+
VHI
I
Vg
VH-
LOW
Magnet
MagnetVH+
Vg
B
HIGH
1.21
0.750
HIGH
1.20
0.745
VH=48V
VH(mV)
VH(mV)
1.19
1.18
1.17
Field sweeping up
Field sweeping down
Vg=3V
1.16
-400
-200
VH=14V
0.735
Field sweeping up
Field sweeping down
Vg=4V
0.730
LOW
1.15
0.740
0
B(Gauss)
200
400
-400
LOW
-200
0
B(Gauss)
200
400
Conclusion, and future direction of research
Conclusion
Switching of ferromagnets detected successfully – switching
field 150 Gauss
 Gate bias modulation of Hall voltage demonstrated
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Future Research
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Shrinking the dimension of HHE device to submicron range
Trying different magnetic material for broader hysteresis loop
Amplifying the output hall voltage
Integrating with MQCA, and fabricate a novel, cost effective,
low power magnetoelectronic device on the same silicon
substrate
Building nonvolatile memory capable of instant ON operation