Characterization of ZnO Films Grown by Chemical Vapor Deposition as Active Layer in Pseudo-MOSFET

The characterization of zinc oxide (ZnO) films, developed by a home-built chemical vapor deposition (CVD) system, working as an active layer for a n-channel depletion mode pseudo-metal-oxide-semiconductor field-effect transistor (MOSFET) is reported. A factorial experimental design was applied to analyze the behavior of the structural, optical, and morphological properties of the ZnO semiconductor. To study the behavior of the assembled equipment, the main parameters of substrate temperature, oxygen flow, and chamber pressure were varied at two levels. The ZnO films were studied by means of the characterization techniques of scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy, photoluminescence, and cathodoluminescence. SEM images showed that the submicrometric ZnO morphologies were obtained from the interaction of the three growth parameters. XRD analysis exhibited an hexagonal wurtzite structure without the presence of other crystalline phases. The Raman response was analyzed according to the dependence of the oxygen flow, temperature, and growth pressure. The emission obtained under ultraviolet laser excitation showed two strong emissions, at 487 nm and 514 nm. In comparison, cathodoluminescence spectra of the ZnO samples exhibited a dominant transition centered at 380 nm. According to the results of the factorial design, one ZnO sample was selected as the active layer for the development of a pseudo-field effect transistor. The transfer and output characteristics of the device were used to study the threshold voltage, carrier mobility, and transconductance behavior. As a result, this work provides an alternative pathway to the fabrication of a n-channel depletion mode ZnO pseudo-transistor using a low-cost and home-built CVD system.