ARC Nanotechnology Network

Prof Pallab Bhattacharya Distinguished Lecturer

Prof Bhattacharya is from the Solid State Electronics Laboratory in the Department of electrical Engineering and Computer Science, at the University of Michigan.

During his visit to Australia, he gave talks at:

  • The Australian National University
  • Macquarie University
  • The University of Melbourne
  • Video Recording

    A video recoding on DVD of the seminar given at the Research School of Physical Sciences and Engineering, ANU Canberra, on Wednesday 13th December 2006, is now available.

    If you would like a complimentary copy of the DVD, please email your name and postal address to:arcnn@ausnano.net

    Full details of Prof Bhattacharya's tour were as follows:

    MELBOURNE on Monday 11 December 2006
    Location:The University of Melbourne
    Conference Room (Level 7) of the School of Physics
    Time: 2:00PM
    Contact:Dr Chris Pakes Tel: (0)3 8344 7816

    CANBERRA on Wednesday 13 December 2006
    Location:ANU
    Leonard Huxley Lecture Theatre, Bldg 56, End of Mills Road
    Time: 11:00AM
    Contact: Ilonka Krolikowska Tel: 02 61252495

    SYDNEY on Friday 15 December 2006
    Location:Macquarie University
    Building E7B, Room 100 (E7B 100)
    Time: 11:00AM
    Contact: Carol McNaught Tel: 02 9850 8911, email: carol@ics.mq.edu.au

    ABSTRACT for the seminar held in Canberra:

    Spin-Based Semiconductor Heterostructure Devices

    Semiconductor spintronics has been the subject of intensive experimental and theoretical investigations aimed at realizing devices which can outperform their charge-based counterparts, yet no commercial applications have been realized to date. To this end, we have studied the processes of spin injection, transport and detection of spin polarized carriers in compound semiconductor based devices consisting of magnetic non-magnetic semiconductor heterostructures.
    Measurements on conventional spin-valves suffer from spurious contributions from anisotsopic magnetoresistance (AMR) and stray Hall voltages arising from the ferromagnetic contacts. We have studied the magnetoresistance of lateral spin-valves fabricated from an epitaxially grown MnAs/GaAs heterostructure and utilizing a Schottky tunnel barrier for efficient spin injection. A coercive field difference between the two ferromagnetic MnAs contacts is obtained by a difference in aspect ratio. Peak magnetoresistances of 3.6% at 10K and 1.1% at 125K are measured for a 0.5m channel length, which is indicative of diffusive spin transport. The agnetoresistance increases with increasing bias and with decreasing temperature. Control experiments have been carried out with non-local spin valves and AMR devices to confirm the spin-valve effect.
    The spin-polarized vertical cavity surface-emitting laser (spin-VCSEL) promises a number of advantages over a conventional VCSEL enhanced intensity and polarization stability as well as a reduced threshold current and has potential applications in cryptographic communications and reconfigurable optical interconnects. We have recently reported the first electrically injected spin VCSEL and a reduction of threshold current in these devices through electrical injection of spin polarized electrons. An electroluminescence polarization of 23% and threshold current reduction of 11% are obtained in an electrically-pumped spin-polarized vertical-cavity surface-emitting laser. Electron spin injection is accomplished utilizing a regrown Fe/n+ Al0.1 Ga0.9 As Schottky tunnel barrier deposited around the base of the laser mesas. Negligible electroluminescence polarizations and threshold current reductions are measured for nonmagnetic and Fe-based control VCSELs, which provides convincing evidence of spin injection, transport, and detection in our spin-polarized laser.
    The properties of these spin-based devices will be described and discussed.