Preparation And Optical Characterization Of ZnSe, ZnTe Films And Quantum Well Structures On Si Substrate By LP-MOCVD

Wide band-gap II-VI materials, such as ZnSe, ZnTe and their alloys attract much attention due to their potential applications in light-emitting devices (LEDs), laser diodes (LDs), optical bistable and optical nonlinear devices operqtynw in blue-green spectrum range for the fact that they exhibit large band gap and high exciton binding energy. Usually, GaAs is employed as substrate for the growth of wide band-gap II-VI semiconductors due to their similarities in lattice constant. However, as a mature semiconductor material, Si has serves electronics greatly. The possibility to combine the photonic materials with Si-based micro-electronic technology motives researchers to devote to the preparation and characterization of wide bandgap II-VI semiconductors on Si substrate.In the present thesis, ZnSe, ZnTe and their quantum well (QW) structures on Si substrates with ZnO as buffer layer by low pressure metal-organic chemical vapor deposition (LP-MOCVD) technique were prepared. ZnO is selected as the buffer layer for it has many similarities with the oxide layer on the surface of Si wafer. All important experimental results and conclusions presented in this thesis aresummarized as follows:1. High quality ZnO films were obtained on Si substrate. ZnO film was grown on N-treated Si substrate by metal-organic plasma-enhanced chemical vap r duposytionO(MO-PECVD) technique, the FWHM of ZnO (0002) was 0.20. The best annealing condition of the ZnO films grown by electron beam evaporationtechnique was achieved.2. ZnSe and ZnTe films were grown on Si substrate by employing ZnO as buffer layer. The effect of the annealing temperature and duration on the structural and optical properties of the ZnSe and ZnTe films was also investigated.3. ZnCdSe/ ZnSe and ZnCdTe/ ZnTe QW structures were grown on ZnO buffered Si substrate. The redshift of the photoluminescence (PL) peak with increasing the well width indicates that ZnCdSe/ ZnSe and ZnCdTe/ ZnTe QW structures were obtained. The surface of ZnCdSe/ ZnSe QW grown on ZnO buffered Si substrate is free of micro-cracks that is observed on the surface of the sample deposited directly on Si substrate. The quantum efficiency of the ZnCdTe/ ZnTe QW structure is distinctly higher than that grown on bare Si substrate.4. The effect of ZnO buffer on the quality of ZnSe, ZnTe and their QW structures was discussed. It was thought that ZnO buffer layer eliminates the imbalance of interface charge and weaken the thermal stress, so that the dislocation between wide band-gap II-VI materials and Si substrate would be decreased.