The LaPierre research group is focussed on the development of semiconductor materials and devices. Our current work focuses on the growth and characterization of group III-V compound semiconductors and their application in photonic and optoelectronic devices including infrared photodetectors and cameras, thermoelectrics, betavoltaics, and quantum information processing (single photon sources, detectors).
We have a wide variety of experimental tools at McMaster:
Centre for Emerging Device Technologies, CEDT (https://www.eng.mcmaster.ca/centre-emerging-device-technologies-cedt-0)
Metalorganic chemical vapour deposition system (MOCVD) for compound semiconductors.
Cleanroom for device fabrication including reactive ion etching, sputtering, photolithography, electron-beam deposition.
Wide variety of materials characterization tools including ellipsometry, micro-photoluminescence, Fourier transform infrared spectroscopy, I-V probe station.
Canadian Centre for Electron Microscopy, CCEM (https://ccem.mcmaster.ca/)
State-of-the-art electron beam characterization including scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, and electron energy loss spectroscopy. Also, focussed ion beam etching/deposition and atom probe tomography are available.
McMaster Analytical X-Ray Diffraction Facility, MAX
A wide variety of x-ray diffraction equipment is available.
Figure 1. Molecular beam epitaxy system for semiconductor growth.
We employ a semiconductor deposition technique (molecular beam epitaxy; Figure 1) for growth of III-V semiconductor alloys containing In, Ga, Al, As, P and Sb (such as GaAs, InP, InSb, InAs, GaP, etc.) and dopants for the formation of p-n junctions (Si, Be, Te). A wide range of deposition, processing techniques and devices are under investigation. Our recent focus has been on the growth, characterization, and device applications of semiconductor nanowires (Figure 2).
Figure 2. (a-c). Scanning electron microscopy images of GaAs nanowire arrays. (d) Transmission electron microscopy image of a single GaP nanowire with GaAs quantum dots/wells. The Ga seed particle, responsible for nanowire growth, is visible as the bright hemisphere at the top (upper right) of the nanowire.
We are seeking both M.A.Sc. and Ph.D. students. Below is a list of potential projects.
Project 1: Metamaterials
Nanowire growth occurs by collection of growth species into a seed droplet (e.g., a Ga droplet for growth of GaAs nanowires). We can control the nanowire morphology (diameter and shape) by manipulating the seed particle during growth of the nanowires (e.g., expanding it or shrinking it). By alternating the growth conditions, we can alternate the nanowire diameter along the length of the nanowires (“hyper-dimensional nanowires”), thereby creating a new type of metamaterial with many applications. One application of these structures is an effective Bragg grating (distributed mirror) for laser cavities. This project involves the simulation of optical properties (reflectance, transmittance, absorptance) of nanowires using COMSOL Multiphysics software.
Relevant literature:
D.P. Wilson and R.R. LaPierre, Corrugated nanowires as distributed Bragg reflectors, Nano Express 3 (2022) 035005.
D.P. Wilson and R.R. LaPierre, Simulation of optical absorption in conical nanowires, Opt. Exp. 6 (2021) 9544.
D.P. Wilson, A.S. Sokolovskii, V.G. Dubrovskii and R.R. LaPierre, Photovoltaic light funnels grown by GaAs nanowire droplet dynamics, IEEE J. Photovolt. 9 (2019) 1225.
Project 2: Thermoelectrics
By creating “corrugated” nanowires (Figure 3), we can create a surface structure and internal crystal phase boundaries that scatter phonons (quantization of lattice vibrations or heat). This would be of great interest in thermoelectric devices that efficiently convert thermal energy into electrical power to be used for the harvesting of waste heat. This project involves the measurement of the thermal properties of nanostructures and development of efficient thermoelectric devices.
Figure 3. (a) Scanning electron microscopy image of a single GaAs nanowire, showing surface faceting due to a twinning superlattice. (b) Transmission electron microscopy image of the superlattice twinning.
Relevant literature:
A. Ghukasyan and R.R. LaPierre, Thermal transport in twinning superlattice and mixed-phase GaAs nanowires, Nanoscale 14 (2022) 6480.
A. Ghukasyan, P. Oliveira, N.I. Goktas and R.R. LaPierre, Thermal conductivity reduction in GaAs nanowire arrays measured by the 3ω method, Nanomaterials 12 (2022) 1288.
A. Ghukasyan, N.I. Goktas, V. Dubrovskii and R.R. LaPierre, Phase diagram for twinning superlattice Te-doped GaAs nanowires, Nano Lett. 22 (2022) 1345.
A. Ghukasyan and R.R. LaPierre,Modelling thermoelectric transport in III-V nanowires using a Boltzmann transport approach: A review, Nanotechnology 32 (2021) 042001.
N.I. Goktas, A. Sokolovskii, V. Dubrovskii and R.R. LaPierre, Unified formation mechanism of twinning superlattices in doped GaAs nanowires, Nano Lett. 20 (2020) 3344.
Project 3: Nuclear nano-battery
Betavoltaics employ a radioactive isotope placed near a semiconductor. Beta particle emission (fast electrons) from the radioisotope results in electron-hole pair generation in the semiconductor. Thus, betavoltaics operate in a manner similar to solar photovoltaics but replace photons with beta particles, generating electrical power by nuclear-to-electrical conversion. Betavoltaic batteries have a very long life (equal to the half-life of the radioisotope) and can operate under a wide variety of environmental conditions (e.g., in the dark, unlike photovoltaics). Thus, betavoltaics have a wide variety of applications such as deep ocean monitoring, sensor networks, space satellites, etc. However, one of the problems with betavoltaics is the very low efficiency of nuclear-to-electrical power conversion (a few percent). Using McMaster’s extensive nuclear engineering facilities, we are developing a novel approach to place radioisotopes in the space between nanostructures to improve the beta capture and betavoltaic device conversion efficiency by about a factor of 10.
Relevant literature:
D.L. Wagner, D.R. Novog and R.R. LaPierre, Genetic algorithm optimization of core-shell nanowire betavoltaic generators, Nanotechnology 31 (2020) 455403.
D.L. Wagner, D.R. Novog and R.R. LaPierre, Design and optimization of nanowire betavoltaic generators, J. Appl. Phys. 127 (2020) 244303.
D. Wagner, D. Novog and R.R. LaPierre, Simulation and optimization of current generation in gallium phosphide nanowire betavoltaic devices, J. Appl. Phys. 125 (2019) 165704.
S. McNamee, D. Novog and R.R. LaPierre, GaP nanowire betavoltaic device, Nanotechnology 30 (2019) 075401.
Invited Review: N.I. Goktas, P. Wilson, A. Ghukasyan, D. Wagner, S. McNamee and R.R. LaPierre, Nanowires for energy: A review, Appl. Phys. Rev. 5 (2018) 041305.
Project 4: Multispectral infrared photodetectors
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. The wavelength of light absorbed by a semiconductor nanowire depends on the nanowire diameter (larger diameters absorb longer wavelengths). By tuning the diameter of nanowires, a multispectral photodetector can be created for advanced infrared imaging systems. 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 multispectral capability integrated into existing Si technology
Relevant literature:
C.J. Goosney, V.M. Jarvis, J.F. Britten and R.R. LaPierre, InAsSb pillars for multispectral long-wavelength infrared absorption, J. Infrared Phys. and Technol. 111 (2020) 103566.
C. Goosney, V.M. Jarvis, D.P. Wilson, N.I. Goktas and R.R. LaPierre, InSb nanowires for multispectral infrared detection, Semicond. Sci. Technol. 34 (2019) 035023.
M. Robson, K.M. Azizur-Rahman, D. Parent, P. Wojdylo, D.A. Thompson and R.R. LaPierre, Multispectral absorptance from large-diameter InAsSb nanowire arrays in a single epitaxial growth on silicon, Nano Futures 1 (2017) 035001.
R.R. LaPierre, M. Robson, K.M. Azizur-Rahman and P. Kuyanov, A review of III-V nanowire infrared photodetectors and sensors, J. Phys. D: Appl. Phys. 50 (2017) 123001.
K.M. Azizur-Rahman and R.R. LaPierre, Optical design of a mid-wavelength infrared InSb nanowire photodetector, Nanotechnology 27 (2016) 315202.
K.M. Azizur-Rahman and R.R. LaPierre, Wavelength-selective absorptance in GaAs, InP and InAs nanowire arrays, Nanotechnology 26 (2015) 295202.
J. Zhang, N. Dhindsa, A.C.E. Chia, J.P. Boulanger, I. Khodadad, S. Saini and R.R. LaPierre, Multi-spectral optical absorption in substrate-free nanowire arrays, Appl. Phys. Lett. 105 (2014) 123113.
Project 5: Quantum computing
Semiconductor quantum dots (Figure 2d) can be implemented along the length of nanowires by changing the material to create heterostructures – for example, by sandwiching a small bandgap segment of GaAs by larger bandgap segments of GaP. These quantum dots are being used as single photon emitters for quantum computing, quantum communications and quantum sensing. This project involves the growth of quantum dot nanowires and optical characterization of the single photon emitters.
Relevant literature:
P. Kuyanov, S.A. McNamee and R.R. LaPierre, GaAs quantum dots in a GaP nanowire photodetector, Nanotechnology 29 (2018) 124003
P. Kuyanov and R.R. LaPierre, Photoluminescence and photocurrent from InP nanowires with InAsP quantum dots grown on Si by molecular beam epitaxy, Nanotechnology 26 (2015) 315202.
An introductory course on nanoelectronics, quantum transport and mesoscopic physics including diffusive and ballistic transport in the classical and quantum regimes, quantum Hall effect, Coulomb blockade, quantum structures, superconductors, topological insulators, and quantum computing.
This course introduces group III-V semiconductor materials, heterostructures and devices including HBTs, HEMTs, laser diodes, photodiodes, and multi-junction solar cells.
3 unit(s) An introduction to quantum optics including single photon states, coherent states, standard quantum limit, Heisenberg limit, squeezed light, entanglement, and applications in metrology.
3 unit(s) An introduction to quantum optics including single photon states, coherent states, standard quantum limit, Heisenberg limit, squeezed light, entanglement, and applications in metrology.
4 unit(s) Introductory statistics for engineering, error analysis of experimental data, data visualization and curve fitting, hypothesis testing and making decisions, ANOVA, sensors for engineering measurements, noise and interference, instrument response and uncertainty, reliability, and selected topics in state-of-the-art technologies.
Three lectures, one lab (three hours) every other week, one tutorial; second term
Prerequisite(s): Registration in Level III or above of any Engineering Physics program and ENGPHYS 2A04, ENGPHYS 2E04, ENGPHYS 2NE3, ENGPHYS 2QM3, and ENGPHYS 3W03.
