Growth and optical study of high quality ZnO, ZnMgO, ZnMnO and ZnCdO

• Main Authors: Chien, Kun-Feng, 簡崑峯
• Other Authors: Chou, Wu-Ching
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/93630033565779941256

博士 === 國立交通大學 === 電子物理系所 === 101 === In this dissertation, the growth of high quality ZnO, ZnMgO, ZnMnO and ZnCdO thin films on Al2O3 substrate by plasma-assisted molecular beam epitaxy were studied. The photoluminescence (PL), transmittance and time-resolved photoluminescence (TRPL) were used to investigate the optical properties. For the growth of Zn1-xMgxO (x=0~0.112) thin films, MgO buffer is used to improve the surface morphology during the initial growth stage, which eventually leads to an atomically flat surface. ZnO/ZnMgO multiple quantum wells were also fabricated successfully on the atomically flat MgO surface. In the case of Zn1-xMnxO (x=0~0.061) thin films, transmittance spectra show an increase of band gap with the increasing Mn concentration. Resonant Raman scattering spectra showed 11 longitudinal optical phonon lines for the Zn1-xMnxO samples. In addition, circular polarization degree of 9 % was observed in the Zn0.997Mn0.003O sample at magnetic field B=5 T. Furthermore, the growth of high quality Zn1-xCdxO thin films with visible light emission was achieved at growth temperature of 350 ℃. The concentration of Cd can be systematically adjusted via the Cd/Zn beam pressure ratio and the maximum concentration was 49.7 %. The origin of radiative recombination and dynamics of the charge carriers in the graded Zn1-xCdxO multilayers was investigated by means of PL and TRPL spectroscopy. The internal quantum efficiency of our sample achieved 33.67 %.