Dr. Ray LaPierre

 

r-lapierre-s

Professor and Department Chair

Department of Engineering Physics

McMaster University
1280 Main Street West, Hamilton
Ontario, Canada
L8S 4L7

Office: JHE/A315/A
Email: lapierr@mcmaster.ca
Phone: (905) 525-9140 x 27764

B.Sc. (Dalhousie), M. Eng. (McMaster), Ph.D. (McMaster), P. Eng

Research:

Our current work focuses on the growth and characterization of semiconductor materials, and their application in solar cells (photovoltaics), photodetectors, infrared cameras, light sources, sensors, quantum information processing, and other optoelectronic devices. We employ a semiconductor deposition technique (molecular beam epitaxy) for growth of III-V semiconductor alloys containing In, Ga, Al, As, P, Sb and N (such as GaAs, InP, InSb, InAs, GaP, etc.). A wide range of deposition, processing techniques and devices are under investigation. Recently, our focus has been on the growth, characterization, and device applications of semiconductor nanowires. We have a large effort to develop third generation solar cells and detectors using nanostructures.

The central challenge in photovoltaic (solar cell) design is the cost-effective conversion of sunlight to electricity over the very broad range of wavelengths present in the solar spectrum. Currently, the vast majority of the photovoltaic (PV) market is made up of silicon (Si) flat panel solar cell modules. This is a relatively mature technology, with commercial flat panels largely manufactured from bulk single-crystal or multi-crystalline Si wafers with typical conversion efficiencies approaching or even exceeding 20%, and approaching the theoretical efficiency limit of 30%. There is therefore a need for innovative thinking to push Si solar cell technology beyond its current limitations. The highest solar cell efficiencies to date have been achieved using thin films of III-V semiconductor materials stacked together in tandem sub-cells connected electrically in series. Power conversion efficiencies of III-V cells are the highest of any technology, reaching over 30% in flat panels and exceeding 44% under concentrated sunlight. However, such devices cannot be grown on Si due to lattice-mismatch, and are generally grown instead on GaAs or Ge substrates that are prohibitively expensive. As a result, the application of III-V materials in terrestrial PV has been very limited. To overcome these limitations, it is highly desirable to combine the high performance of III-V materials with the relatively low cost and mature Si technology, thereby achieving the best of both worlds. To achieve this goal, recent work in photovoltaics is beginning to exploit intentionally engineered III-V semiconductor nanowire arrays that can be grown directly on Si. Our work has shown that a III-V nanowire array integrated with Si is capable of 34% PV efficiency (1 Sun) or 42% under concentrated light (500 Suns). Despite these advantages, the best reported efficiency for III–V nanowire arrays is much lower than their expected efficiency. The reasons for such modest performance are presently unclear, and further research in this field is needed. We are investigating all aspects of III-V nanowire growth on Si to produce a high efficiency, low cost solar cell technology.

We are also developing III-V nanowires monolithically integrated with Si and their potential in wavelength tunable infrared cameras. III-V nanowires support optical resonant modes such that nanowires act as very effective waveguides that concentrate and absorb light over a length of only a few microns, enabling very efficient photodetectors and solar cells with relatively little material. It is also of great interest to develop multi-spectral or wavelength discriminating infrared detectors or cameras for advanced infrared imaging systems. The resonant absorption in nanowires shows wavelength selectivity that can be tuned continuously across the visible and infrared wavelengths by adjusting the nanowire diameter. This principle can be used as a new concept for multi-spectral imaging. Lattice-mismatched III-V nanowires can be grown directly on Si substrates enabling integration with existing Si CCD or CMOS sensors. These capabilities enable large-area, low cost infrared sensors with multi-spectral capability integrated into existing Si technology.

Publications:

2014:
83. S.M. Jovanovic, G.A. Devenyi, V.M. Jarvis, K. Meinander, C.M. Haapamaki, P. Kuyanov, M. Gerber, R.R. LaPierre, and J.S. Preston, Optical characterization of epitaxial single crystal CdTe thin films on Al2O3 (0001) substrates, Thin Solid Films 570 (2014) 155.
82. J. Walia, N. Dhindsa, J. Flannery, I. Khodabad, J. Forrest, R.R. LaPierre, and S.S. Saini, Diameter dependent photo-thermal effects in vertically etched GaAs nanowire arrays, Nano Lett. 14 (2014) 5820.
81. S.J. Gibson and R.R. LaPierre, Model of patterned self-assisted nanowire growth, Nanotechnology 25 (2014) 415304.
80. J. Zhang, N. Dhindsa, A.C.E. Chia, J.P. Boulanger, I. Khodadad, S. Saini and R.R. LaPierre, Direct measurement of multi-spectral optical absorption in nanowire arrays, Appl. Phys. Lett. 105 (2014) 123113.
79. J.P. Boulanger, A.C.E Chia and R.R. LaPierre, Gallium loading of gold seed for high yield of patterned GaAs nanowires, Appl. Phys. Lett. 105 (2014) 083122.
78. A. Darbandi, O. Salehzadeh, P. Kuyanov, R. R. LaPierre and S. P. Watkins, Surface passivation of tellurium-doped GaAs nanowires by GaP: Effect on electrical conduction, J. Appl. Phys. 115 (2014) 234305.
77. N. Dhindsa, A. Chia, I. Khodadad, R.R. LaPierre and S.S. Saini, Highly ordered vertical GaAs nanowire arrays with dry etching and their optical properties, Nanotechnology 25 (2014) 305303.
76. J. Zhang, A. Chia and R.R. LaPierre, Low resistance indium tin oxide contact to n-GaAs nanowires, Semicond. Sci. Technol. 29 (2014) 054002.
75. J.P. Boulanger and R.R. LaPierre, Unveiling transient GaAs/GaP nanowire growth behavior using group V oscillations, J. Cryst. Growth 388 (2014) 116.

2013:
74. M. Fanetti, S. Ambrosini, Matteo Amati, L. Gregoratti, M.K. Abianeh, A. Franciosi, A.C.E. Chia, R.R. LaPierre and S. Rubini, Spatially resolved monitoring of the Fermi-edge position inside the energy gap: a tool for local investigation of doping in nanowires, J. Appl. Phys. 114 (2013) 154308.
73. S.J. Gibson, J.P. Boulanger and R.R. LaPierre, Opportunities and pitfalls in patterned self-catalyzed GaAs nanowire growth on silicon, Semicond. Sci. Technol. 28 (2013) 105025.
72. A.C.E Chia, M. Tirado, F. Thouin, R. Leonelli, D. Comedi and R.R. LaPierre, Surface depletion and electrical transport model of AlInP-passivated GaAs nanowires, Semicond. Sci. Technol. 28 (2013) 105026.
71. A.C.E Chia and R.R. LaPierre, Electrostatic model of radial pn junction nanowires, J. Appl. Phys. 114 (2013) 074317.
70. N. Gupta, Y. Song, G.W. Holloway, U. Sinha, C.M. Haapamaki, R.R. LaPierre and J. Baugh, Temperature-dependent electron mobility in InAs nanowires, Nanotechnology 24 (2013) 225202.
69. S.J. Gibson and R.R. LaPierre, Study of radial growth in patterned self-catalyzed GaAs nanowire arrays by gas source molecular beam epitaxy, Physica Status Solidi RRL 7 (2013) 845.
68. Feature article on journal front cover, R.R. LaPierre, A.C.E. Chia, S.J. Gibson, C.M. Haapamaki, J. Boulanger, R. Yee, P. Kuyanov, J. Zhang, N. Tajik, N. Jewell and K.M.A. Rahman, III-V nanowire photovoltaics: Review of design for high efficiency, Phys. Status Solidi RRL 7 (2013) 815.
67. Y.A. Pusep, H. Arakaki, C.A. de Souza, A. D. Rodrigues, C.M. Haapamaki and R. R. LaPierre, Crystal structure and optical characterization of heterostructured GaAs/AlGaAs/GaAs nanowires, J. Appl. Phys. 113 (2013) 164311.
66. G.W. Holloway, Y. Song, C.M. Haapamaki, R.R. LaPierre and J. Baugh, Electron transport in InAs-InAlAs core-shell nanowires, Appl. Phys. Lett. 102 (2013) 043115.
65. Y. Hu, M. Li, J.-J. He and R.R. LaPierre, Current matching and efficiency optimization in a two-junction nanowire-on-silicon solar cell, Nanotechnology 24 (2013) 065402.
64. G.W. Holloway, Y. Song, C.M. Haapamaki, R.R. LaPierre and J. Baugh, Trapped charge dynamics in InAs nanowires, J. Appl. Phys. 113 (2013) 024511.

2012:
63. R.J. Yee, S.J. Gibson, V.G. Dubrovskii and R.R. LaPierre, Effect of Be doping on InP nanowire growth mechanisms, Appl. Phys. Lett. 101 (2012) 263106.
62. A.C.E. Chia, J.P. Boulanger and R.R. LaPierre, Unlocking doping and compositional profiles of nanowire ensembles using SIMS, Nanotechnology 24 (2013) 045701.
61. Y. Hu, R.R. LaPierre, M. Li, K. Chen and J.-J. He, Optical characteristics of GaAs nanowire solar cells, J. Appl. Phys. 112 (2012) 104311.
60. C. M. Haapamaki, R. R. LaPierre and J. Baugh, Critical shell thickness for InAs-AlxIn1−xAs(P) core-shell nanowires, J.
Appl. Phys. 112 (2012) 124305.
59. Feature article on journal front cover, N. Tajik, C.M. Haapamaki and R.R. LaPierre, Photoluminescence model of sulfur passivated p-InP nanowires, Nanotechnology 23 (2012) 315703.
58. N. Tajik, A.C.E. Chia and R.R. LaPierre, Improved conductivity and long-term stability of sulfur-passivated n-GaAs nanowires, Appl. Phys. Lett. 100 (2012) 203122.
57. A.C.E. Chia and R.R. LaPierre, Analytical model of surface depletion in GaAs nanowires, J. Appl. Phys. 112 (2012) 063705.
56. K. Chen, J.-J. He, M. Li and R.R. LaPierre, Fabrication of GaAs nanowires by colloidal lithography and dry etching, Chinese Phys. Lett. 29 (2012) 036105.
55. A.C.E Chia, M. Tirado, Y. Li, S. Zhao, Z. Mi, D. Comedi and R.R. LaPierre, Electrical transport and optical model of GaAs-AlInP core-shell nanowires, J. Appl. Phys. 111 (2012) 094319.
54. N.C. Vega, R. Wallar, J. Caram, G. Grinblat, M. Tirado, R.R. LaPierre and D. Comedi, ZnO nanowires co-growth on SiO2 and C by vapour advection and Au-catalyzed deposition, Nanotechnology 23 (2012) 275602.
53. J.P. Boulanger and R.R. LaPierre, Patterned gold-assisted growth of GaP nanowires on Si, Semicond. Sci. Technol. 27 (2012) 035002.
52. C.M. Haapamaki, J. Baugh and R.R. LaPierre, Facilitating growth of InAs-InP core-shell nanowires through the introduction of Al, J. Cryst. Growth 345 (2012) 11.

2011:
51. C.M. Haapamaki and R.R. LaPierre, Molecular beam epitaxy growth mechanisms in InAs/InP nanowire heterostructures, Nanotechnology 22 (2011) 335602.
50. J.P. Boulanger and R.R. LaPierre, Polytype formation in GaAs/GaP axial nanowire heterostructures, J. Cryst. Growth 332 (2011) 21.
49. R.R. LaPierre, Theoretical conversion efficiency of a two-junction nanowire on Si solar cell, J. Appl. Phys. 110 (2011) 014310.
48. Y.A. Pusep, A. Gold, M.C. Mamani, M. Godoy, Y.G. Gobato and R.R. LaPierre, Electron and hole scattering in short-period InGaAs/InP superlattices, J. Appl. Phys. 110 (2011) 073706.
47. Feature article on journal front cover, A.C.E. Chia and R.R. LaPierre, Contact planarization of ensemble nanowires, Nanotechnology 22 (2011) 245304.
46. N. Tajik, Z. Peng, P. Kuyanov and R.R. LaPierre, Sulfur passivation and contact methods in GaAs nanowire solar cells, Nanotechnology 22 (2011) 225402.
45. R.R. LaPierre, Numerical model of current-voltage characteristics and efficiency of GaAs nanowire solar cells, J. Appl. Phys. 109 (2011) 034311.
44. P. K. Mohseni, G. Lawson, A. Adronov, and R. R. LaPierre, Hybrid GaAs nanowire-carbon nanotube flexible photovoltaics , IEEE JSTQE 17 (2011) 1070.

2010:
43. V. Jarvis, J.F. Britten and R.R. LaPierre, Texture analysis of GaAs nanowires, Semicond. Sci. Technol. 26 (2011) 025014.
42. Feature article on journal front cover, J. Baugh, J.S. Fung, J. Mracek, and R.R. LaPierre, Building a spin quantum bit register using semiconductor nanowires, Nanotechnology 21 (2010) 134018.
41. H. A. Budz, M. Ali, Y. Li, R. R. LaPierre, A hybrid aptamer-GaAs optical biosensor, J. Appl. Phys. 107 (2010) 104702.
40. A. Fakhr, Y.M. Haddara and R.R. LaPierre, Dependence of InGaP nanowire morphology and structure on molecular beam epitaxy growth conditions, Nanotechnology 21 (2010) 165601.
39. Y.A.Pusep, P.K. Mohseni, R.R. LaPierre, A.K.Bakarov, and A.I.Toropov, A study of disorder effects in random (AlxGa1-xAs)n(AlyGa1-yAs)m superlattices embedded in a wide parabolic potential, Appl. Phys. Lett. 96 (2010) 113106.
38. J. Caram, C. Sandoval, M. Tirado, D. Comedi, J. Czaban, and R. R. LaPierre, Electrical characteristics of core-shell p-n GaAs nanowire structures with Te as the n-dopant, Nanotechnology 21 (2010) 134007.
37. E. De Jong, R.R. LaPierre, and J. Z. Wen, Detailed modeling of the epitaxial growth of GaAs nanowires, Nanotechnology 21 (2010) 045602.
36. M. Tirado, D. Comedi, and R.R. LaPierre, Impedance spectroscopy characterization of GaAs nanowire bundles grown by metal-catalyzed molecular beam epitaxy, J. Alloys and Compounds 495 (2010) 443–445.
35. D. Comedi, M. Tirado, C. Zapata, S. P. Heluani, M. Villafuerte, P. Mohseni, and R.R. LaPierre, Randomly oriented ZnO nanowires grown on amorphous SiO2 by metal-catalyzed thermal evaporation, J. Alloys and Compounds 495 (2010) 439–442.

2009:
34. P.K. Mohseni, A.D.Rodrigues, J.C.Galzerani, Y.A. Pusep, and R.R. LaPierre, Structural and optical analysis of GaAsP/GaP core-shell nanowires, J. Appl. Phys. 106 (2009) 124306.
33. H. Bi and R.R. LaPierre, A GaAs nanowire/P3HT hybrid photovoltaic device, Nanotechnology 20 (2009) 465205.
32. M.C. Plante and R.R. LaPierre, Analytical description of the metal-assisted growth of III–V nanowires: axial and radial growths, J. Appl. Phys. 105 (2009) 114304.
31. H.A. Budz, M.C. Biesinger and R.R. LaPierre, Passivation of GaAs by octadecanethiol self-assembled monolayers deposited from liquid and vapor phases, J. Vac. Sci. Technol. B 27 (2009) 637 .
30. S. C. Ghosh, P. Kruse, and R. R. LaPierre, Effect of GaAs (100) surface preparation on growth of nanowires, Nanotechnology 20 (2009) 115602.
29. J.A. Czaban, D.A. Thompson, and R.R. LaPierre, GaAs core-shell nanowires for photovoltaic applications, Nano Lett. 9 (2009) 148.
28. P.K. Mohseni and R.R. LaPierre, A growth interruption technique for stacking fault-free nanowire superlattices, Nanotechnology 20 (2009) 025610.

2008:
27. Y.A. Pusep, G.C. Gozzo, and R.R. LaPierre, Interface roughness in short-period InGaAs/InP superlattices, Appl. Phys. Lett. 93 (2008) 242104.
26. P.K. Mohseni, G. Lawson, C. Couteau, G. Weihs, A. Adronov and R.R. LaPierre, Growth and characterization of GaAs nanowires on carbon nanotube composite films: towards flexible nano-devices, Nano Lett. 8 (2008) 4075.
25. M.C. Plante and R.R. LaPierre, Control of GaAs nanowire morphology and crystal structure, Nanotechnology 19 (2008) 495603.
24. H.A. Budz and R.R. LaPierre, Properties of octadecanethiol self-assembled monolayers deposited on GaAs from liquid and vapor phases, J. Vac. Sci. Technol. A 26 (2008) 1425.
23. C. Chen, N. Braidy, C. Couteau, C. Fradin, G. Weihs, and R.R. LaPierre, Multiple quantum well AlGaAs nanowires, Nano Lett. 8 (2008) 495-499.
22. M.C. Plante and R.R. LaPierre, Au-assisted growth of GaAs nanowires by gas source molecular beam epitaxy: tapering, sidewall faceting and crystal structure, J. Cryst. Growth 310 (2008) 356-363.

2007:
21. P.K. Mohseni, C. Maunders, G.A. Botton, and R.R. LaPierre, GaP/GaAsP/GaP core-multishell nanowire heterostructures on (111) silicon, Nanotechnology 18 (2007) 445304.
20. C. Chen, S. Shehata, C. Fradin, C. Couteau, G. Weihs, and R.R. LaPierre, Self-directed growth of AlGaAs core-shell nanowires for visible light applications, Nano Lett. 7 (2007) 2584.
19. D.M. Cornet and R.R. LaPierre, InGaAs/InP core-shell and axial heterostructure nanowires, Nanotechnology 18 (2007) 385305.
18. S.C. Ghosh, M.C. Biesinger, R.R. LaPierre, and P. Kruse, X-ray photoelectron spectroscopic study of the formation of catalytic Au nanoparticles on ultraviolet-ozone oxidized GaAs(100) substrates, J. Appl. Phys. 101 (2007) 114322.
17. S.C. Ghosh, M.C. Biesinger, R.R. LaPierre, and P. Kruse, The role of proximity caps during the annealing of ultraviolet-ozone oxidized GaAs, J. Appl. Phys. 101 (2007) 114321.
16. D.M. Cornet, V.G.M. Mazzetti, and R.R. LaPierre, Onset of stacking faults in InP grown by gas source molecular beam epitaxy, Appl. Phys. Lett. 90 (2007) 013116.

2006:
15. C. Chen, M.C. Plante, C. Fradin, and R.R. LaPierre, Layer-by-layer and step-flow growth mechanisms in GaAsP/GaP nanowire heterostructures, J. Mater. Res. 21 (2006) 2801-2809.
14. M.C. Plante, J. Garrett, S.C. Ghosh, P. Kruse, H. Schriemer, T. Hall, and R. R. LaPierre, The formation of supported monodisperse Au nanoparticles by uv/ozone oxidation process, Appl. Surf. Sci. 253 (2006) 2348-2354.
13. D.M. Cornet, R.R. LaPierre, D. Comedi, and Y.A. Pusep, High resolution x-ray diffraction analysis of InGaAs/InP superlattices, J. Appl. Phys. 100 (2006) 043518.
12. Y.A. Pusep, A.G. Rodrigues, J.C. Galzerani, D. Comedi, and R.R. LaPierre, Evidence of the miniband formation in InGaAs/InP superlattices, Brazilian J. Physics 36 (2006) 905.
11. Y.A. Pusep, A.G. Rodrigues, J.C. Galzerani, D.M. Cornet, D. Comedi, and R.R. LaPierre, Miniband effect on optical vibrations in short-period InGaAs/InP superlattices, Phys. Rev. B 73 (2006) 235344.
10. M.C. Plante and R.R. LaPierre, Growth mechanisms of GaAs nanowires by gas source molecular beam epitaxy, J. Cryst. Growth 286 (2006) 394-399.

2005:
9. R.R. LaPierre and M.C. Plante, Potential for novel magnetic structures by nanowire growth mechanisms, J. Magnetics 10 (2005) 108-112.

1999-2004:
My work from 1999-2004 was conducted in an industrial context and is considered intellectual property of JDS Uniphase Inc. External publications are not available in these instances due to the proprietary nature of the work, although a substantial number (~50) of internal publications and technical reports were produced.

1995-1998 (Publications associated with my graduate work):
8. R. R. LaPierre, D. A. Thompson and B. J. Robinson, Reduction of composition modulation of InGaAsP grown by atomic-hydrogen-assisted epitaxy producing improved double-heterostructure laser performance, Semicond. Sci. Technol. 13 (1998) 637.
7. R. R. LaPierre, D. A. Thompson and B. J. Robinson, Evaluation of plasma and thermal sources for atomic hydrogen-assisted epitaxy of InP, J. Vac. Sci. Technol. A 16 (1998) 590.
6. R. R. LaPierre, B. J. Robinson and D. A. Thompson, Growth mechanisms of III-V compounds by atomic hydrogen-assisted epitaxy, J. Cryst. Growth 191 (1998) 319.
5. R. R. LaPierre, B. J. Robinson and D. A. Thompson, The role of atomic hydrogen in argon plasma-assisted epitaxy of InGaAsP/InP, J. Vac. Sci. Technol. B 15 (1997) 1707.
4. R. R. LaPierre, B. J. Robinson and D. A. Thompson, Group V incorporation in InGaAsP grown on InP by gas source molecular beam epitaxy, J. Appl. Phys. 79 (1996) 3021.
3. R. R. LaPierre, T. Okada, B. J. Robinson, D. A. Thompson and G. C. Weatherly, Lateral composition modulation in InGaAsP strained layers and quantum wells grown on (100) InP by gas source molecular beam epitaxy, J. Cryst. Growth 158 (1996) 6.
2. R. R. LaPierre, T. Okada, B. J. Robinson, D. A. Thompson and G. C. Weatherly, Spinodal-like decomposition of InGaAsP/(100) InP grown by gas source molecular epitaxy, J. Cryst. Growth 155 (1995) 1.
1. R. R. LaPierre, B. J. Robinson and D. A. Thompson, Lateral composition modulation of InGaAsP deposited by gas source molecular beam epitaxy on (100) and (h11)-oriented InP substrates, Appl. Surf. Sci. 90 (1995) 437.