ZnS, ZnSe Films And ZnSe Quantum Dots Grown By MOCVD

Wide band-gap II-VI semiconductor materials such as ZnS, ZnSe have been thought as one of the most import materials for their potential in the optoelectronic . devices. If the epitaxial growth technique was used, the wide band-gap II-VI semiconductor materials epitaxial grown on Si substrates can lead to the possibility to combine the advantages of Si in microelectronics with the characterization of wide band-gap II-VI semiconductor materials in optoelectronics.In this thesis, the ZnS, ZnSe films and ZnSe quantum dots(QDs) have been obtained by metalorganic chemical vapor deposition(MOCVD). The following is the major results:1 ZnS epilayers directly grown on Si substrate was obtained by low-pressure metalorganic chemical vapour deposition(LP-MOCVD), in which hydrogen sulphide(H2S) and dimethylzinc (DMZn) were used as the reactants. No high-temperature pre-heat-treatment of the Si substrate was used to obtain epilayers. The ZnS epilayer quality was improved with decreasing the substrate temperature. The small X-ray diffraction FWHM was obtained at 300, which implied that the ZnS epilayers had higher quality. The atom ratio of Zn/S was close to 1:1 .which showed that the ZnS epilayers had good stoichiometry.2 ZnSe epilayers on Si substrate were obtained by LP-MOCVD, in which hydrogen selenium(H2Se) and dimethylzinc (DMZn) were used as the reactants. The effect of the flow rate of Zn/Se one the epilayer quality of ZnSe was discussed. The results indicated that DMZn flow rate predominately controlled the growth rate of ZnSe epilayer in this work. The atomic ratio of Zn/Se was close to 1:1, which showed that the ZnSe epilayers had good stoichiometry. A strong blue near-band-gap photoluminescence(PL) peak of ZnSe epilayers was observed at 77K without any additional PL signal at longer wavelengths. This indicated an absence of deep trapping centers. This peak was still observed at room temperature, temperature. The presence of this intrinsic near-band-gap emission line in the PL spectrum even at room temperature is a further indication for the high quality of the epitaxial layer.3 The five-cycle ZnSe/ZnS quantum structure samples grown on Si substrate were obtained under V-W mode by LP-MOCVD. The blueshift at 77K PL increased with the decrease in ZnSe growth duration. The temperature-dependent PL was studied. The FWHM of PL decreased with increasing temperature at first, then it increased with increasing temperature. This is one of the characteristic of quantum dots(QDs), which showed that the samples we obtained on Si substrate by LP-MOCVD were ZnSe QDs.4 I took part in the system reformation item of Chinese Academy of Sciences as the major member- the reformation of photo-assisted MOCVD system. In order to test the photo-assisted MOCVD system we reformed, the ZnSe and ZnSe:N films were grown by using this photo-assisted MOCVD system.