Magneto-Optical Studies of IndiumGalliumArsenic Quantum Wells and Devices used for Spintronics Applications
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Spintronics has been one of the most rapidly developing research areas in condensed matter physics. Exploiting the electron’s spin degree of freedom is hoped to yield new and novel technological applications. The ability to generate a non-equilibrium spin population, to manipulate the spins, and to be able to detect them have been the most intensely studied subjects in this research area. In this dissertation, spin injection from an Fe (Iron) ferromagnetic spin polarizing contact into two dimensional semiconductor hetero-structures were investigated using a device called a "Spin-LED" also known as a Spin Light Emitting Diode. Due to its high Curie temperature, Fe is a very promising candidate for practical applications at room temperature. This dissertation is comprised of two separate experimental studies outlined as follows. (1) We have investigated the Polarization of the Spin LEDs as function of Bias. In addition to the exciton we see a feature called "LV" (Low Voltage) that is bias and temperature dependent. We have compared the Spin life time TS measured for the exciton, LV feature in the device (Spin LED) and for the exciton in the unprocessed InGaAs QW. The LV feature shows polarization in excess of 70% and the polarization changes sign as we increase the magnetic field from B = 0 Tesla to B = 7 Tesla. (2) We see intensity oscillations in for the photoluminescence for exciton in the InGaAs QWs. We attribute these oscillations to the Optical Aharonov-Bohm effect. A shift in the oscillations has been observed when the sample relative angle with respect to the magnetic field is changed. These oscillations are present only in the Faraday’s geometry and disappear in the Voigt geometry.