Improvement of conductivity in GaSe:Zn thin films grown by MBE

• Main Authors: Yen-chi Wang, 王彥其
• Other Authors: Chu-shou Yang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/25885262352348783154

碩士 === 大同大學 === 光電工程研究所 === 103 === In this study, high-conductivity GaSe:Zn thin films grown on a c-sapphire substrate are achieved using molecular beam epitaxy (MBE). The thin films are monitored by reflection high energy electron diffraction (RHEED). The streaky RHEED patterns which imply the growing thin film has high crystal quality along the [0001] azimuth are observed after 5 minutes since start growing. As the zinc atom content increasing in GaSe, the growth rate increases nearing twice than undoped GaSe, which implies that its growth mechanism is different from undoped GaSe. There are several shifts of peak (004) in X-ray diffraction (XRD) spectra, implying that the exceeding zinc content would induce the formation of ZnSe crystal and effect on lattice constant in GaSe:Zn condition. In Raman measurements, at lightly doped condition, E''(LO) mode suddenly disappeared. However, with increasing TZn, E''(LO) mode appeared again and this phonon energy is the same as ZnSe (LO). According to the previous suggestion of the exist ZnSe, this peak is assign to ZnSe (LO). The layer-by-layer structure is directly observed by high resolution transmission electron microscopy (HRTEM). Conductivity of the best sample is 1.6×10-4 (Ω×cm)-1 measured by Four Point Prober and flexible sample B is taken from substrate by general tape.