The LaPierre research group is focussed on semiconductor materials and device physics. Our current work focuses on the growth and characterization of group III-V compound semiconductor materials, and their application in infrared photodetectors and cameras, thermoelectrics, betavoltaics, quantum information processing (quantum sources, detectors) and other optoelectronic devices and applications.
We have a wide variety of experimental tools available, including:
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.
We employ a semiconductor deposition technique (molecular beam epitaxy) 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.
We are developing group III-V compound semiconductor nanowires for various photonic and optoelectronic applications. These semiconductor nanowires are grown by molecular beam epitaxy (MBE) using a selective-area self-assisted growth process. 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).
Project 1:
By alternating the growth conditions, we can alternate the nanowire diameter along the length of the nanowires (“hyper-dimensional nanowires”), thereby creating an effective Bragg grating for nanowire lasers. We are interested in digital control of the nanowire morphology for spectral engineering. This project involves the simulation of optical properties (reflectance, transmittance, absorptance) of nanowires using COMSOL Multiphysics software, and the fabrication of the simulated structures.
Relevant articles:
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:
By creating “corrugated” nanowires, we can create a surface structure that scatters 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 setup of a measurement system to study the thermal properties of individual nanowires using Raman spectroscopy.
Relevant articles:
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. Betavoltaics 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). We are developing a novel approach to place radioisotopes in the space between nanowires to improve the betavoltaic conversion efficiency by about a factor of 10.
Relevant articles:
D.L. Wagner, D.R. Novog and R.R. LaPierre, Genetic algorithm optimization of core-shell nanowire betavoltaic generators, Nanotechnology 31 (2020) 455403.
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:
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. We are also fabricating nanowire structures for mid-wavelength and long-wavelength photodetectors by etching nanowires from InSb and InAsSb thin films. Nanowires can be etched from a thin film, using either reactive ion etching or focused ion beam etching. Some preliminary devices have already been fabricated. We are interested in further device fabrication and characterization.
Relevant articles:
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.
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:
Semiconductor quantum dots 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.
Relevant articles:
P. Kuyanov, S.A. McNamee and R.R. LaPierre, GaAs quantum dots in a GaP nanowire photodetector, Nanotechnology 29 (2018) 124003
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.
