Department of Physics, Panjab University, Chandigarh, India

TPSC seminar

Time and date: 23 August 2012 (Thursday), 4:00 pm
Venue: Seminar Hall

Title: Polarization resolved optical and magneto-optical studies on III-V semiconductor bulk and quantum well structures

Speaker: Mr. Ashish Arora, Department of Condensed-Matter Physics and Material Science, TIFR, Mumbai

Abstract: The technological world that we see around us today, would never have been the same if there were no semiconductors and semiconductor devices. The various portable devices that we own today, e.g. mobile phones, calculators, personal computers or laptops, all entertainment gadgets like music players, LED TVs, the world lit of LEDs, the traffic light controls and much more wouldn't have been simply there if there were no semiconductors. Integration of transistors on a single chip has been a boon to the technological world, and this miniaturization doesn't seem to come to an end, still continuing at the same pace as it was when it started in early 1960s. Polarization resolved spectroscopic measurements on semiconductors and their nanostructures provide useful information regarding their electronic band structure (EBS). We discuss two examples, one where a sample is under strain and another where it is under an external magnetic field. In the first example, linear polarization resolved lateral-photoconductivity measurements on specially fabricated GaAs/AlGaAs quantum well (QW) device structures demonstrate that anisotropic strain present in the plane of the QW leads to valence band mixing which modifies the transition selection rules, giving riseto in-plane polarization anisotropy. Thereafter we discuss the case of GaAs/AlGaAs QWs and bulk GaN under magnetic fields whose influence on the EBS is to introduce Landau levels and Zeeman splitting. We show that a sensitive way of probing the spin-split EBS is through magneto-optical Kerr effect (MOKE) spectroscopy. This technique enables determination of very small excitonic Zeeman splittings and helps determine Lande g-factors in QWs under low magnetic fields (< 1.8T). A well width dependent study of electron-heavy hole and electron-light hole exciton g-factors is presented and compared with k.p theory based calculations.