Magneto-optical studies of III-V and II-VI nanostructures
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In this thesis we describe magneto-optical studies of three semiconductor heterostructures. In the first study we have recorded the electroluminescence (EL) from Fe spin light emitting diodes (spin-LEDs) in which the intrinsic wide GaAs quantum well (QW) is populated by holes. The emission characteristics from this system is compared with those from Fe spin-LEDs in which the GaAs QW is populated by electrons, studied earlier. In the second project we have studied the magneto-EL spectra from a LED in which the GaAs quantum wells in the intrinsic region of the device are populated by a dense two-dimensional electron gas. This experiment yielded spin splittings of the h1 valence sub-band Landau levels. The third project involved a magneto-photoluminencence (PL) study of ZnMnTe quantum dots (QDs) embedded in a ZnSe matrix. This system shows evidence of the spontaneous formation of a polaron. At low temperatures the polaron consists of an electron in the ZnSe matrix, a hole and a Mn ion in the ZnMnTe QD. The emission at low temperatures is strongly circularly polarized (σ+ or σ-). As the temperature is raised the polarization drops to zero. This is interpreted as due a breakdown of the e-h-Mn polaron into an electron and a h-Mn polaron that persists up to room temperature. Aharonov-Bohm oscillations in the PL intensity have been observed in this system.