Q.Y. Chen

Epitaxial n-ZnO on p-Si with native SiO x reduced by Al overlayer

RF magnetron sputtering has been employed to deposit n-type epitaxial zinc oxide thin films on p-type silicon substrates to form p-n diode structures. Native SiOx layers, Commonly found on silicon, typically of a few nanometer thick, would hinder the epitaxial growth of ZnO. In this work, a crystalline metal oxide overlayer was introduced as a buffer by imposing a reduction reaction on the SiOx layer via oxidation of the metal.

Growth and characterization of III-nitride based multiple quantum wells for photovoltaic devices

Efficient conversion of solar energy into electricity is crucial to the use of renewable energy. Among the various semiconductors being investigated for photovoltaic conversion, III- nitrides are fervently pursued because of their band gap tenability from 0.65 eV to 3.4 eV by adjusting the indium concentration of InXGa1-XN alloys. This enables the coverage of optical absorption over a wide range of the solar spectrum, thus providing a path to boosting the conversion efficiency. This presentation reports on multiple quantum well (MQW) based solar cells fabricated on LiGaO2 (001) substrates by plasma assisted molecular beam epitaxy (PA-MBE). Metal-modulated-epitaxy (MME) technique was utilized to prevent formation of metal droplets during the material growth. Streaky patterns, seen in reflection high energy electron diffraction (RHEED), indicate 2-dimensional (2D) growth throughout the device. Post-deposition characterizations using scanning electron microscopy (SEM) showed smooth surfaces, while X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the epitaxial nature of the quantum well structure.