Growth Of Gaas (111) Surface Quantum Well Materials And Their Optical And Electrical Properties

Firstly, the theory and fabrication of molecular beam epitaxy(MBE) are described in detail. The surface morphology of InAs/GaAs quantum dot was studied by using atomic force microscopy (AFM). A series of high Al composition AlGaAs films at GaAs (111) substrate grown by MBE were investigated by using room temperature photoluminescence spectra, low temperature photoluminescence spectra. Secondly, when the GaAs epitaxial layer grows on the GaAs (111) substrate, the single and double periods of RHEED intensity oscillation will be changed under different growth conditions. By means of RHEED oscillations, high quality quantum wells grown on GaAs (111) have been found under optimized growth conditions. The influence of different growth conditions on electron spin relaxation time in GaAs/AlGaAs (111) quantum wells (QWs) grown by MBE has been investigated by room temperature photoluminescence spectra, time-resolved Kerr rotation spectroscopy(TRKR), low photoluminescence spectra. The main content is as follows:1. The growth temperatures,the growth velocity and As2/Ga beam equivalent pressure ratios (BEP) have an important impact on the growth of high Al composition Al0.3Ga0.7As films at GaAs (111) substrate with high crystal quality and good optical property. In this report, we grown a series of samples with different growth temperatures and different BEP ratios on GaAs (111) substrates by molecular beam epitaxy. The samples were investigated by using room temperature photoluminescence spectra, low temperature photoluminescence spectra. Then, the optimized growth condition was found on the growth of Al0.3Ga0.7As films at GaAs (111) substrates.2. When the GaAs epitaxial layer grows on the GaAs (111) substrate, there are two growth modes (monolayer-by-monolayer and bilayer-by-bilayer) under different conditions that correspond to monolayer and bilayer RHEED (Reflection High Energy Electron Diffraction) oscillations. The measurements of transmission electron microscope and photoluminescence at room temperature showed that the quantum wells had very bad optical property under the bilayer-by-bilayer growth mode, while the quantum wells grown under the monolayer-by-monolayer growth mode had much better optical property with rough interfaces. By means of RHEED oscillations, high quality quantum wells grown on GaAs (111) have been found under optimized growth conditions.3. The influence of interface growth interruption on electron spin life timeτin GaAs/AlGaAs (111) quantum wells (QWs) grown by solid source molecular beam epitaxy (SSMBE) has been investigated by room temperature photoluminescence spectra and time-resolved Kerr rotation spectroscopy (TRKR). The growth interruption at double interruption mode (GaAs-on-AlGaAs and AlGaAs-on-GaAs) interface had a more impact on electron spin life time in QWs than that at inverted (AlGaAs-on-GaAs) interface. Various interface interruption time were used in growing QWs. Interface roughness of these QWs samples was studied by room temperature photoluminescence spectra. The photoluminescence spectra indicated that interface roughness decreased as the interface growth interruption time increased. TRKR measurements at room temperature showed that the appropriate growth interruption could increase spin life time in GaAs/AlGaAs QWs drastically. This dramatic increase was explained by the suppression of the D'yakonov-Perel' interaction.