Fabrication of Nanodot Decorated Sapphire Substrates for Abbreviated Growth Mode Deposition of ...

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Lehigh University
Lehigh Preserve
Theses and Dissertations
2013
Fabrication of Nanodot Decorated Sapphire
Substrates for Abbreviated Growth Mode
Deposition of Gallium Nitride
Jeffrey Biser
Lehigh University
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Biser, Jeffrey, "Fabrication of Nanodot Decorated Sapphire Substrates for Abbreviated Growth Mode Deposition of Gallium Nitride"
(2013).Theses and Dissertations.Paper 1429.
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Fabrication of Nanodot Decorated Sapphire Substrates for
Abbreviated Growth Mode Deposition of Gallium Nitride

by

Jeffrey M. Biser

Presented to the Graduate and Research Committee
of Lehigh University
in Candidacy for the Degree of
Doctor of Philosophy

in
Materials Science and Engineering

Lehigh University
May 2013
DISSERTATION SIGNATURE SHEET

Approved and recommended for acceptance as a dissertation in partial fulfillment of
the requirements for the degree of Doctor of Philosopy.

_______________________
Date
_______________________
Accepted Date
Committee Members:

_______________________
Prof. Richard P. Vinci
(Committee Chair)
_______________________
Prof. Helen M. Chan
_______________________
Prof. Walter Brown
_______________________
Prof. Nelson Tansu
_______________________
Prof. Volkmar Dierolf

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ACKNOWLEDGEMENTS:
First, I would like to thank my advisor, Rick Vinci. It is a weak tautology to
simply say that without an advisor, one could not receive a doctorate. But the fact
that without this particular person in this particular position, I would not be
defending this work, is far less trivial. Through surprising results, fickle equipment,
bad luck, better luck, and all the general vicissitudes of scientific endeavor which
caused this grad student’s career to extend to a full decade, Rick has been an
unflagging source of motivation and mental clarity.
I also owe a large debt of gratitude to my committee members, Professors
Helen Chan, Nelson Tansu, Walter Brown, and Volkmar Dierolf, for always being
available for support and willing to schedule things in a pinch when deadlines loomed
large on the horizon.
I thank my family, Mom and Dad and Kris and Tony, for being pillars of sanity
and ungrudging charity when everything seemed at best crazy and at worst hopeless.
For cooperation in the lab on many occasions, I must thank my colleagues in
Rick’s group: Nick Barbosa, Paul El-Deiry, Rich Chromik, Seung-Min Hyun, Sreya
Dutta, Hongwei Li, Jason Perkins, Wanjun Cao, Kittisun Mongkolsuttirat, and Mark
MacLean. I must also thank my co-collaborators Yik-Khoon Ee and Xiaohang Li from
Prof. Tansu’s group in ECE. I fought with the sapphire, they fought with the GaN
reactor, and somehow we managed to get some nice devices made. Thanks also to
Dave Ackland, Rob Keyse, Bill Mushock, Arlan Benscoter, Sam Lawrence, Mike Rex,
and Gene Kozma for assistance with all manner of things. Thanks to Maxine, Deanne,
Anne Marie, and Katrina for keeping all the paperwork from becoming
overwhelming.
The faculty and staff at CNF were crucial to this project at the sample fab
stage. Thanks are due to Daron Westly, Michael Skvarla, Alan Bleier, Aaron Windsor,
Rob Ilic, Meredith Metzler, and Kathy Springer.
To The Manhattan Project (Cheers, gentlemen). To Loopers’ and Molly’s and
Sandra’s and the Funhouse. To the whole cohort of southsiders and westsiders and
northsiders.
And to all those whom space prevents me naming here… Thanks!
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TABLE OF CONTENTS:

Certificate of Approval .................................................................................................. ii
Acknowledgements ..................................................................................................... iii
Table of Contents ......................................................................................................... iv
List of Figures ............................................................................................................... vii

ABSTRACT ...................................................................................................................... 1

CHAPTER 1: REVIEW OF GALLIUM NITRIDE BASED SOLID STATE LIGHTING ................. 2
1.1: Foreword ..................................................................................................................... 2
1.2: LED Luminaires for Solid-State Lighting ...................................................................... 2
1.3: Gallium Nitride Based Optics: LEDs and Quantum Well Lasers .................................. 5
1.4: Architecture of LED Based SSL Luminaires .................................................................. 7
1.5: Critical Factors for Luminaire Efficiency ...................................................................... 8
1.6: Compound Semiconductors and Growth Techniques ............................................... 11
1.7: Threading Dislocation and Defect Reduction Strategies ........................................... 13

CHAPTER 2: ABBREVIATED GROWTH MODE TECHNIQUE FOR III-V
SEMICONDUCTORS .............................................................................. 17
2.1: Foreword ................................................................................................................... 17
2.2: Fabrication of Sapphire Nanodots via Conversion of Aluminum .............................. 18
2.3: Preparation of Substrates for GaN Growth ............................................................... 21
2.4: Fabrication of GaN Based MQW-LEDs at Lehigh ....................................................... 23
2.5: Abbreviated Epitaxial Growth Mode (AGM) ............................................................. 26
2.6: Remaining Substrate Fabrication Issues .................................................................... 31

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CHAPTER 3: A NOVEL TECHNIQUE FOR LARGE AREA PATTERNING VIA POROUS
ANODIC ALUMINUM OXIDE ............................................................................ 33
3.1: Foreword ................................................................................................................... 33
3.2: Large Area Patterning Techniques ............................................................................ 34
3.3: New AAO Liftoff Mask for Aluminum on Sapphire ................................................... 38
3.4: Improving Uniformity of AAO Patterned Structures ................................................. 42

CHAPTER 4: SIZE-DEPENDENT SURVIVAL AND MORPHOLOGICAL ALTERATION OF
NANODOTS DURING CONVERSION ................................................................. 44
4.1: Foreword ................................................................................................................... 44
4.2: Preliminary Observation of Disappearance and Morphological Change .................. 45
4.3: Survey Of Relevant Properties and Behaviors of Aluminum and its Oxide ............... 50
4.3.1: “Thermal Timeline” ..................................................................................... 50
4.3.2: Phase Transformations and Thermodynamic Considerations .................... 52
4.3.3: Substrate Traction Forces and Hillocking .................................................... 54
4.3.4: Surface Diffusion and Wetting..................................................................... 57
4.3.5: Evaporation ................................................................................................. 60
4.3.6: Oxidation of Aluminum at Elevated Temperatures ..................................... 65
4.4: Experimental Design and Procedure ......................................................................... 71
4.4.1: Rationale ...................................................................................................... 71
4.4.2: Experimental Procedures ............................................................................ 74
4.4.2.1. Fabrication ....................................................................................... 74
4.4.2.2. Oxidation Heat Treatment ............................................................... 78
4.4.2.3. Characterization ............................................................................... 79
4.5: Observations and General Trends ............................................................................. 84
4.5.1: Summary of SEM observations .................................................................... 84
4.5.2: Summary of TEM observations.................................................................... 89
4.6: Analysis of Results ..................................................................................................... 90
4.6.1: Failure Mechanisms ..................................................................................... 90
4.6.2: Optimum Processing Conditions for AGM................................................... 96
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CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS ............................................. 99
5.1: Summary of Impact ................................................................................................... 99
5.2: Suggestions for Future Work ................................................................................... 102
5.2.1: AGM Development .................................................................................... 102
5.2.2: Large-area Substrate Development ........................................................... 103
5.2.3: Aluminum-to-Alumina Conversion ............................................................ 104

LIST OF REFERENCES .................................................................................................. 106
AUTHOR’S BIOGRAPHY .............................................................................................. 110

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LIST OF FIGURES:

FIGURE 1: HISTORICAL AND PREDICTED EFFICIENCY OF LIGHT SOURCES. ................... 4
FIGURE 2: COMPARISON OF THE LIGHT OUTPUT POWER FOR GREEN-EMITTING
STAGGERED INGAN QUANTUM WELL LEDS AND CONVENTIONAL
INGAN QUANTUM WELL LEDS. .............................................................. 7
FIGURE 3: TILTED SEM IMAGE OF HILLOCKING IN CONTINUOUS 100 NM THICK
ALUMINUM FILM ON SAPPHIRE AFTER ANNEALING TO 450 °C. (SCALE
BAR IS 10 ΜM) ...................................................................................... 19
FIGURE 4: FIB-CUT CROSS-SECTION OF ALUMINUM METALLIZATION ON SAPPHIRE
NESTED WITHIN UNDERCUT PMMA RESIST PRIOR TO LIFTOFF... ........ 22
FIGURE 5: DEVICE SIZED PATCHES OF ALUMINUM NANODOTS ON SAPPHIRE (PRIOR
TO CONVERSION). ................................................................................. 24
FIGURE 6: SEM OF NANOPATTERNED SAPPHIRE REGION WITH GAN BUFFER LAYER
GROWTH INTERRUPTED AT 15 NM. ..................................................... 27
FIGURE 7: ROOM TEMPERATURE CONTINUOUS WAVE LIGHT OUTPUT POWER AS A
FUNCTION OF INJECTION CURRENT OF INGAN QW LEDS GROWN ON
THREE COMPARISON GAN TEMPLATES. .............................................. 28
FIGURE 8: TIME RESOLVED PHOTOLUMINESCENCE MEASUREMENTS OF INGAN QW
LED DEVICES GROWN ON DIFFERENT GAN FILMS. .............................. 28
FIGURE 9: FIB-CUT CROSS-SECTIONAL TEM IMAGE OF ALUMINA NANODOT ON
SAPPHIRE SUBSTRATE COATED WITH AGM-GAN. ............................... 30
FIGURE 10: ROOM TEMPERATURE CW LIGHT OUTPUT POWER AS A FUNCTION OF
INJECTION CURRENT OF INGAN QW LEDS GROWN ON THREE
COMPARISON TEMPLATES. .................................................................. 30
FIGURE 11: TILTED SEM OF SAPPHIRE NANODOTS USED IN PITCH STUDY................. 31
FIGURE 12: SEM CROSS-SECTION OF AAO FILM FORMED BY SINGLE ANODIZATION TO
COMPLETION OF AN ALUMINUM FILM ON GLASS. ............................. 37
FIGURE 13: SEM TOP VIEW OF AAO FILM FROM FIGURE 12. ..................................... 37
FIGURE 14: AAO FILM ON SAPPHIRE AFTER RIE TREATMENT TO OPEN PORE
BOTTOMS. ............................................................................................ 40
FIGURE 15: SEM OF UNDERSIDE OF AAO MASK AFTER LIFTOFF, DEMONSTRATING
EFFECTIVE PORE OPENING AT PORE BOTTOMS. .................................. 41
FIGURE 16: TILTED SEM IMAGE OF ALUMINUM DOTS ON SAPPHIRE FORMED VIA
AAO LIFTOFF TECHNIQUE. .................................................................... 42
FIGURE 17: ALUMINUM NANODOTS OF ~ 80 NM (TOP) AND ~ 120 NM (BOTTOM)
DIAMETER AFTER LIFTOFF (LEFT) AND ANNEALING AT 450 °C FOR 24
HOURS (RIGHT). .................................................................................... 47
FIGURE 18: ALUMINUM NANODOTS FROM FIG. 15 AFTER ANNEALING AT 1200 °C
FOR 24 HOURS. ..................................................................................... 48
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FIGURE 19: ALUMINUM NANODOTS AFTER ANNEALING AT 450 °C FOR 24 HR (LEFT),
FOLLOWED BY 1200 °C FOR 24 HR (RIGHT). ......................................... 48
FIGURE 20: ALUMINUM NANODOTS WITH VARYING INITIAL DIAMETER AFTER 1300
°C FOR 1 HR. .......................................................................................... 49
FIGURE 21: "THERMAL TIMELINE" OF CRITICAL EVENTS DURING ANNEALING OF
ALUMINUM AND ITS OXIDE .................................................................. 50
FIGURE 22: MELTING POINT OF ALUMINUM (CELSIUS) MEASURED VERSUS APPLIED
PRESSURE (KG/CM2 = ~ 100 KPA) IN DRY ARGON (1) AND DRY
NITROGEN (2). ...................................................................................... 53
FIGURE 23: IN-PLANE STRESS AT FILM EDGE. ............................................................. 56
FIGURE 24: PLOT OF SURFACE DIFFUSIVITY D AND CORRESPONDING
S
CHARACTERISTIC DIFFUSION LENGTH D FOR 1 HOUR. ........................ 58
FIGURE 25: EVAPORATION FLUX FROM ALUMINUM BASED ON EMPIRICAL VAPOR
PRESSURE DATA. ................................................................................... 61
FIGURE 26: LIFETIME OF AN ALUMINUM NANODOT OF A GIVEN SIZE, AT VARIOUS
TEMPERATURES (IN °C), BASED ON EVAPORATION DATA. .................. 63
FIGURE 27: ILLUSTRATION OF CONCEPTUAL EVAPORATION MODES. ....................... 65
FIGURE 28: EVAPORATION LIFETIME AT 1082 °C FOR MODES DESCRIBED IN FIG. 27.
.............................................................................................................. 65
FIGURE 29: SPMS DATA FROM PARK ET AL. EXHIBITING DEGREE OF COMPLETION OF
OXIDATION FOR ALUMINUM NANOPARTICLES AT FOUR
TEMPERATURES. ................................................................................... 70
FIGURE 30 SUMMARY OF EXPECTED AL DOT BEHAVIORS AT VARIOUS TEST
TEMPERATURES. ................................................................................... 73
FIGURE 31: WAFER LAYOUT FOR EBL AT CNF. ............................................................. 75
FIGURE 32: SEM IMAGE OF ~ 80 NM DIAMETER ALUMINUM NANODOTS AFTER
FABRICATION. ....................................................................................... 80
FIGURE 33: SEM IMAGE OF ~ 210 NM DIAMETER ALUMINUM NANODOTS AFTER
FABRICATION. ....................................................................................... 81
FIGURE 34: PLATINUM PROTECTIVE LAYER DEPOSITED OVER DOTS TO BE CROSS-
SECTIONED (COURTESY OF DR. P. CANTWELL). ................................... 82
FIGURE 35: TEM SAMPLE COUPON ATTACHED TO PLUCKER, READY FOR REMOVAL
(COURTESY OF DR. P. CANTWELL). ....................................................... 83
FIGURE 36: PLUCKED AND THINNED COUPON CONTAINING FOUR DOTS IN CROSS-
SECTION, THINNED TO 300NM FOR ELECTRON TRANSPARENCY
(COURTESY OF DR. P. CANTWELL). ....................................................... 83
FIGURE 37: MAP OF PHENOMENA OBSERVED AFTER ANNEALING AT FOUR PROCESS
TEMPERATURES WITH DIAMETERS RANGING FROM 50 TO 240 NM.
.............................................................................................................. 85
FIGURE 38: SEM IMAGE, UN-TILTED, EXHIBITING POSSIBLE CAVITATION AND CLEAR
FACETING IN ~ 120 NM DOTS ANNEALED AT 1200 °C FOR 1 HOUR. ... 86
viii
FIGURE 39: SEM IMAGE EXHIBITING HILLOCKING / LARGE PROTRUSIONS IN ~ 200
NM DOTS ANNEALED FOR 1 HOUR AT 900 °C, TILTED TO 40°. ............ 87
FIGURE 40: SEM EVIDENCE OF "SLUMPING" IN DOTS WITH ~ 80 NM INITIAL
DIAMETER.. ........................................................................................... 89
FIGURE 41: BRIGHT-FIELD TEM IMAGE OF HOLLOW DOT AFTER 1 HOUR AT 900 °C
(COURTESY OF DR. P. CANTWELL). ....................................................... 90

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