Wireless Hydrogen Sensor Networks Using GaN-Based Devices

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3 Wireless Hydrogen Sensor Networks Using GaN-Based Devices Fan Ren 1, Jenshan Lin 2, Stephen Pearton 3, Hung-Ta Wang 1, Changzhi Li 2, Zhen Ning Low 2, Xiaogang Yu 2, Travis Anderson 1, and Byoung Sam Kang 1, and John Painter 4 1 University of Florida, Chemical Engineering 2 University of Florida, Electrical and Computer Engineering 3 University of Florida, Materials Science and Engineering 4 J Painter Consulting LLC, Deltona, FL 32738

4 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:

5 NASA Funded Hydrogen Research at UF Research Thrust Areas Fuel Cells (PEM and SOFC) Hydrogen Production, Storage, and Transport Nano Sensors - Hydrogen Leak Detection Gas inlet H 2 Gas outlet H 2 Production PEM FC micro grids & Cooling Plate Single Crystal Nanowires Hydrogen-Selective Sensing at Room Temperature with ZnO Nanorods

6 Application fields: Fuel leak detection for automobile, space shuttle, and aircraft. Fire detection (CO, CO 2 ). Emission, hydrocarbon, and health monitor. Environmental control. Motivation

7 Why AlGaN/GaN HEMT? GaN device technology is commercially available (blue LED) Wide range band gap( ev) for high temperature operation Outstanding mechanical and electronic properties Chemical inertness (only NaOH at 450 o C), harsh environment High electron mobility without impurity scattering- fast response - excellent sensitivity-signal amplification Different sensors can be integrated in a single chip AlGaN GaN

8 GaN Diode Fabrication Ti/Al/Pt/Au Pt Ti/Au SiN x Al 0.28 Ga 0.72 N GaN 2DEG 50 µm Sapphire Optical microscopic image Device Cross-section

9 H 2 2H Diffusion of H Creation of a polarized layer at the interface Barrier-lowering Sensing Mechanism Hs H b Hi H 2 Pd, Pt Semiconductor Hi Hs H b H 2 (gas) 2H S 2H b 2H i

10 Experimental Results Current (ma) Nitorgen 1% Hydrogen Biased Voltage (V) J F ** 2 qφb ev = A T exp exp 1 kt nkt ;?? B ~ -50 room T

11 GaN/AlGaN HEMT Sensor for Hydrogen Ti/Al/Pt/Au Ti/Au Pt AlGaN GaN Sapphire Source Gate Drain Source

12 Hardware Design AC Wall Transformer Regulator Battery/Energy Harvest Regulator Internet Cell Phone Battery Backup Control Microcontroller Reference R0 1MΩ 2MΩ Sensor + R0 1MΩ + 2MΩ Vout ZigBee Transceiver Internet Server Wireless Network Server

13 State flow diagram of level monitoring Initialization SLEEP NO Timer set? YES Collect Data Analyze Data NO Threshold Detected? YES Transmit Pulse Monitor Monitor Monitor Monitor Tx data Tx data Tx data Tx data Power Up Power Down Warm up: 30 seconds 5s 1s 5s 1s 5s 1s 5s 1s

14 Robust Detection of Hydrogen Using AlGaN/GaN HEMT Sensing Diodes

15 Sensor 1 Above Car Bay

16 Sensors 4 And 6 Above Bus Bay

17 Field Test

18 Practical Problem-False Alarm Current (ma) Room temperature 50 C Nitrogen 1% Hydrogen Biased Voltage (V) 1. Thermal effect on semiconductor and Schottky contact. 2. Voltage drift

19 Differential Diodes Optical microscopic image

20 Robust Detection of Hydrogen Using Differential AlGaN/GaN Sensing Diodes

21 Wireless Monitoring of Hydrogen Detection

22 Wireless Sensor Module Client can deactivate alarm

23 Wireless ph Remote version 1.1 Sensor Power Management Battery MSP430F2013 Nordic 2.4Ghz Transceiver Features Reconfigurable over-the-air Ultra-low-power 2.4Ghz wireless Rechargeable battery Different sensors can be implemented with minimal design changes

24 Conclusions GaN-based sensors demonstrate rapid response (<1s) and reversibility Differential sensor devices eliminate sensitivity to temperature and voltage drifts TiB 2 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

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