no slide titlebens/presentweb.ppt · ppt file · web view · 2000-11-07space vacuum epitaxy...

Space Vacuum Epitaxy CenterUniversity of HoustonNASA Commercial Space Center

Compact III-V Nitrides-Based Integrated Multifunctional Optoelectronic Sensors for Contaminant Characterization

in Enclosed Space Environments.

A. Bensaoula, D. Starikov, I . Berishev, N. Badi, N. Medelci, J.-W. Um, and A. Tempez

Nitride Materials and Devices ProjectProf. Bensaoula: [email protected]

Dr. Starikov: [email protected]

Outline:• Introduction

• Current Project objectives• Results of the first 5 month work

• Objectives and goals for project continuation• Preliminary results on Nitride materials growth on Si

• Conclusions•Acknowledgements




Advantages of fluorescence:

• High sensitivity• Simplicity• High specificity• Low cost• Multifunctionality (detection, concentration, temperature, flow)

Optical sensors are based on:• Absorption/Reflection (ppm)

• Scattering: Turbidimetry (ppm), Nephelometry (ppb)

• Fluorescence/Phosphorescence/Luminescence (ppt)

Laboratory type fluorescence system




Currently Used Commercial Sensors

Device Sensitivity Range Source Detector ApplicationsWetStarFluorometer,Wetlabs, Inc.

0.03 g/L 0.03-75g/L

2 blue LEDs(455 nm)

Silicon PDDetection:695 nm

Measures chlorophyll innatural waters

ECOAFLxx/DFLFluorometer,Wetlabs, Inc.

20 g/L 100g/L 2 blue LEDs(1kHz)

Silicon PDDetection:695 nm

Detects and measuresphytoplankton biomassand chlorophyll

ECO-VSFScattering SensorWetlabs, Inc.

0.01 m-1 4000counts

Blue (455 nm),green (530nm), and red(650 nm)LEDs

Solar-blindsilicondetector

Detects and measuresconcentration of solidparticles in water

TD-4100 XDFluorometer,Turner Designs

1 g/L 1µg/L ->1000mg/L

LP Hg Lamp(4 W)350-400 nm

PMT(300-650nm)

Detects BTEX,gasoline, diesel, jet fueland oil in industrial,waste, ground, andpotable water

TD-360Fluorometer,Turner Designs

0.5 g/L 0.5-5g/L LP Hg Lamp,blue (460 nm)and green (525nm) LEDs

Silicon PD(300-1100nm)

Measures DNA in thepresence of proteins,RNA, and nucleotides.




WetStarFluorometer

ECO-VSF Scattering Sensor ECO Fluorometer

Advantages and potential sensor applications of III-V Nitrides

• UV applications (wide bandgap)

• Higher efficiency (direct band)

• Possibility to tune the band gap from 1.9 to 6.2 eV (InGaN, AlGaN compounds)

• High thermal stability (up to 600 °C)

• High mechanical and chemical stability







Current project objectives:• Development of compact integrated optoelectronic sensors based on III-V Nitrides grown by RF MBE for contaminants characterization• Implementation of Ionwerks’ Time of Flight Mass Spectrometer for characterization of gaseous environments• Integration of the optoelectronic sensor with the Time of Flight Mass Spectrometer for contaminants characterization of enclosed space environments




300 400 500 600 700

0

20

40

60

80

100 Spectra of a GaN-based Schottky barrier diode:

Photosensitivity Avalanche emission Injective emission

Inte

nsity

(arb

. un.

)

Wavelength (nm)

Development and fabrication of LEDs and photodiodes integrated on a single substrate

UV power: ~466 WBand: 200- 400 nm

Diameter: 0.6 mmReverse bias: 22 V




Experiments with Time of Flight Mass Spectrometer

128 130 132 134 136 138 140 142 144 146 148

50

100

150

200C2

35Cl237Cl

& NC35Cl3

mass (u)

cou

nts

116 117 118 119 120 121 122 1230

2000

4000

6000

Standard RIE PA-RIE

calibrated on Ar

coun

ts

103 104 105 106 107 108 109 110 111 112

50

100

150

BCl2

C235Cl2

35Cl237Cl

coun

ts

80 82 84 86 88 90 92 94 96 980

800

1600

2400

C335Cl2

37Cl

& NC235Cl3

C37Cl3C35Cl37Cl2

C35Cl237Cl

& N35Cl3

C235Cl3

C237Cl2

C235Cl37Cl

C335Cl3

35Cl3

C35Cl3

cou

nts

79 80 81 82 83 84 85 86 87 88 890

50

100

150

200

250

mass (u)

10B37Cl2

11B37Cl35Cl

11B37Cl2

10B35Cl210B37Cl35Cl

11B35Cl2

counts

TOF-MS Cl2/Ar plasma spectra TOF-MS BCl3/Ar plasma spectra

• High resolution: m/m = 800• 4 orders of magnitude of dynamic range,• Low background • Detection limit: <1 ppm for 400msec scan

PA-RIE curve (red) is shifted for illustrative purposes




Advantages of III-V Nitrides growth on commercial silicon wafers

• Much lower fabrication costs

• Compatibility with standard Si processing equipment

• Employment of Si-based junctions in the optoelectronic structure that can extend the spectral range into the visible and IR regions

• Possibility of integration with other silicon-based semiconductor devices or Micro Opto- Electro-Mechanical Systems (MOEMS)




New objectives for the TSGC project continuation• Improve the epitaxial growth of III-V Nitrides on commercial silicon wafers

• Optimize the fabrication process of the optoelectronic structure grown on Si (growth,RIE, contact deposition)

• Evaluate characteristics of the fabricated fluorescence sensors (application range, sensitivity, dynamic range)

• Investigate possibilities of integration of the fluorescence sensors with other MOEMS developed on silicon




Preliminary results on Nitride materials growth on Si

-10 -5 0 5 10-0.02

0.00

0.02

0.04

0.06

0.08

0.10

Cur

rent

(A)

Voltage (V)

250 300 350 400 450 500 550 600 650 700 750

0

20

40

60

80 Spectra of blue LEDs based on GaN/InGaN heterostructures grown on (111) Si wafers

9.8 V, 0.074 A 10.5 V, 0.079 A 11.3 V, 0.084 A

Inte

nsity

(arb

. u.)

Wavelength (nm)

200 250 300 350 400 450 500 550 600 650

0

20

40

60

80

100

120

Inte

nsity

(arb

.u.)

Wavelength (nm)

I-V characteristic of aGaN/InGaN p-n junctiondiode heterostructuregrown on Si wafer

Spectral sensitivity of a GaN/InGaNdiode heterostructure grown on Si




Collaborators• IonwerksIonwerks has over thirteen years experience in manufacturing and marketing a complete surface analysis systems including pulsed beam lines, vacuum hardware, and custom electronics. Recent additions to the product line have evolved from the research interests in TOF ion scattering and mass spectroscopy of recoiled ions (MSRI) which have been developed over the last several years. The new time of flight data and ion detector system was developed around a 4 channel Time-to-Digital Converter (TDC). In the fall of 1996 the compony began marketing a novel reflectron ToF analyzer which is capable of performing surface analysis using both secondary ion mass spectroscopy (SIMS) and mass spectroscopy of recoiled ions (MSRI). All elements, including H, can be identified, with isotopic resolution using SIMS and MSRI. This instrument was recently named a 1997 R&D 100 award winner and is now operating at Argonne National Labs, University of North Carolina Chapel Hill, and University of Houston.




Conclusions

• Spectrally matched light emitting and photosensitive Schottky diode structures have been fabricated on a sapphire substrate

• Ionwerks’ TOF mass spectrometer exhibited high resolution, wide dynamic range, low background, and high sensitivity for measurements performed on BCl2/Cl2/Ar plasmas.

• Blue emission and photosensitivity have been observed on diode structures fabricated from Nitride material layers grown on a single commercial silicon wafer

Acknowledgements:

•Texas Space Grant Consortium Program

• NASA cooperative agreement, # NCC8-127

• Ionwerks’ NASA Phase II SBIR contact monitored by Mr. J. Watkins

• Environmental Institute of Houston, University of Houston

• Institute of Space Systems and Operations

• Texas Advanced Technology Program




no slide titlebens/presentweb.ppt · ppt file · web view · 2000-11-07space vacuum epitaxy...

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