university of florida nha hydrogen conference, march 21, 2007 wireless hydrogen sensor networks...

University of Florida NHA Hydrogen Conference, March 21, 2007

Wireless Hydrogen Sensor Networks Using GaN-based Devices

Travis Anderson1, Hung-Ta Wang1, Byoung Sam Kang1, Fan Ren1, Changzhi Li2, Zhen Ning Low2,

Jenshan Lin2, Stephen Pearton3

1 University of Florida, Chemical Engineering 2 University of Florida, Electrical and Computer Engineering 3 University of Florida, Materials Science and Engineering


NASA Funded Hydrogen Research at UF

• $10M funding over 4 years• 27 Projects• 60 Faculty members, post-docs, and graduate

students combined

UF NASA Funded Hydrogen Research Web Site:

http://www.mae.ufl.edu/NasaHydrogenResearch


NASA Funded Hydrogen Research at UF

Research Thrust Areas

• Fuel Cells (PEM and SOFC)

• Hydrogen Production, Storage, and Transport

• Nano Sensors - Hydrogen Leak DetectionGas inlet

H2

Gas outlet Single Crystal NanowiresHydrogen-Selective

Sensing at Room Temperature with ZnO

NanorodsH2 ProductionPEM FC micro grids & Cooling Plate


Motivation

Application fields:• Fuel leak detection for

automobile, space shuttle, and aircraft.

• Fire detection (CO, CO2).

• Emission, hydrocarbon, and health monitor.

• Environmental control.


Group III Nitride

• Outstanding mechanical and electronic properties

• Controllable wide range band gap(3.4eV-6.2eV AlGaN)

• High thermal stability

• Chemical inertness

• AlGaN/GaN 2DEG for high power and high frequency.


Device Fabrication

50 µm

Optical microscopic image

GaN

Sapphire

Al0.28Ga0.72N

Ti/AuPt

SiNx

Ti/Al/Pt/Au

Device Cross-section

2DEG


Sensing Mechanism

• H22H(chemisorption on Pt)

• Diffusion of H atom.

H2(gas) 2Hs 2Hb 2Hi

• Creation of a polarized layer at the interface

• Decrease of barrier height. (Schottky diode); increase of channel cross-section. (FET)

H2

Hs

Hb

2DEG

HiPt

AlGaN

GaN


Experimental Results

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0

4

8

12

16

20

Cu

rren

t (m

A)

Biased Voltage (V)

Nitorgen

1% Hydrogen

1expexp2**F

nkT

eV

kT

qTAJ B ; ΔФB~ -50 meV @ room T


Practical Problem-False Alarm

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0

4

8

12

16

20

Cu

rren

t (m

A)

Biased Voltage (V)

Nitrogen

1% Hydrogen

Room temperature 50 °C

1. Thermal effect to semiconductor and Schottky contact.

2. Voltage drift


Differential Diodes

Optical microscopic image


1% Hydrogen Test


Hardware Design

Warm up: 30 seconds 1s5s

Monitor

Tx data

Monitor

Tx data

Monitor

Tx data

Monitor

Tx data

Power Up

Power Down

1s5s 1s5s 1s5s


Wireless Sensor Module

Client can deactivate alarm


Field Test


Conclusions

GaN-based sensors demonstrate rapid response (<1s) and

reversibility Differential sensor devices eliminate sensitivity to

temperature and voltage drifts TiB2 can be used in ohmic contacts to improve reliability These sensors have been implemented in a wireless

detection circuit Field testing is underway at Greenway Ford, Orlando, FL We are seeking investors for a startup company


Acknowledgements

This work at UF is supported by:

1. NSF (CTS-0301178, monitored by Dr. M.

Burka and Dr. D. Senich)

2. NASA Kennedy Space Center Grant NAG

10-316 monitored by Mr. Daniel E. Fitch.


Hydrogen Sensing Test

Schematic illustration of gas sensor system


Room Temperature Test


50 °C Test


Comparison of Pd and Pt

Reference:[1] W. Eberhardt, F. Greuter, E. W. Plummer, Phys. Rev. Lett. 46, 1085 (1981).[2] http://www.rebresearch.com/H2sol2.htm[3] http://www.rebresearch.com/H2perm2.htm

[2]

[1][3]


Gas Sensing Devices

Resistor[3]Schottky diode [1] HEMT[2][1] B. S. Kang, F. Ren, B. P. Gila, C. R. Abernathy and S. J. Pearton, Appl. Phys. Lett. 84 1123 (2004).

[2] B. S. Kang, R. Mehandru, S. Kim, F. Ren, R. C. Fitch, J. K. Gillespie, N. Moser, G. Jessen, T. Jenkins, R. Dettmer, D. Via, A. Crespo, B.

P. Gila, C. R. Abernathy and S. J. Pearton, Appl. Phys. Lett. 84 4635 (2004).

[3] H. T. Wang, B. S. Kang, F. Ren, L. C. Tien, P. W. Sadik, D. P. Norton, S. J. Pearton, Jenshan Lin, Appl. Phys. Lett. 86 243503 (2005).

university of florida nha hydrogen conference, march 21, 2007 wireless hydrogen sensor networks...

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