1. 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

2. Gated HHE Device – Structure and Physics
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
Fringing field
Ferromagnet
Gate
2DEG Si Vg Vg
VH+
VH-
Change in magnetization direction (M) => Change in sign of Hall voltage (VH+ to VH-)
Change in gate voltage (Vg) => Change in magnitude of Hall voltage
e- e- M M I I
e- e-
VH-
VH+

3. HHE device – magnetoelectronic system
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

4. HHE device-interfacing MQCA
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
MQCA Array
Spin direction equivalent to logic “0”
Spin direction equivalent to logic “1”
Proposed device-MQCA interfaced with HHE devie

5. Fabrication of HHE device-I
Hall Bar defined in thick (240nm) field oxide by image reversal and mesa etch.
Metal (Ti/W) gate defined on top of Hall Bar, and n-wells formed through ion implantation
Field oxide
P type Si
Gate metal
Gate oxide
n well
n well

6. Fabrication of HHE device-II
Gold bonding pads formed by image reversal and lift-off
Supermalloy deposited on top of the gate by e-beam lithography
Metal bond pad
n well
n well
Supermalloy
n well
n well

7. 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
Magnet
HHE device
Magnetic domains in the ferromagnet

8. Bistable Hall voltage and gate bias modulation
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+
VH- I I
VH-
VH+
LOW Vg
Magnet Vg
Magnet B

9. Conclusion, and future direction of research
Switching of ferromagnets detected successfully – switching field 150 Gauss
Gate bias modulation of Hall voltage demonstrated
Future Research
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