Abstract
Abstract In this thesis we report the studies of optical properties of ZnMnSe/ZnSeTe multiple quantum wells. Quite interesting results have been obtained from our studies which should be very useful for our understanding and application of these materials. Ⅰ. Novel properties of photoluminescence in type-II ZnMnSe/ZnSeTe multiple quantum wells The optical properties of type-II ZnMnSe/ZnSeTe multiple quantum wells were investigated by photoluminescence. From the photoluminescence (PL) spectra, a giant blueshift of the peak energy under moderate excitation power has been observed. It can be well interpreted in terms of the band-bending effect due to spatially separated photoexcited carriers in a type-II band alignment. In addition, a large optical anisotropy of ZnMnSe/ZnSeTe multiple quantum wells (MQWs) has been discovered. Based on the studies of the dependences of excitation intensity and temperature, we point out that the observed anisotropy is an inherent property of the type-II band alignment in ZnMnSe/ZnSeTe MQWs. Ⅱ. Thickness dependence of optical properties of ZnMnSe/ZnSeTe multiple quantum wells Photoluminescence spectra and Raman scattering were performed to study thickness dependence of optical properties of ZnMnSe/ZnSeTe multiple quantum wells. Strong photoluminescence associated with iso-electronic Te traps was observed. As the thickness of the ZnSeTe layer decreases to 1 nm the mechanism of luminescence changes. In Raman spectra, the LO and TO phonons of ZnSeTe layer were observed. A blueshift of optical phonon modes was observed as the thickness of the ZnSeTe decreases. This phenomenon can be well interpreted in terms of the compressive strain effect.
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