ZnMgO thin films for deep ultraviolet applications: structural and optical approach
On February 17, in an online seminar Dr. Ramūnas Nedzinskas (ISSP UL) talks about ZnMgO thin films for deep ultraviolet applications: structural and optical approach.
Abstract:
Light emitters and photodetectors operating in deep-ultraviolet (DUV) photon energy region, are in great demand for while-light generation, environmental protection, high-density data storage, solar-blind detection, germicidal irradiation, etc. Wide-bandgap semiconductors, such as AlGaN, ZnMgO, diamond, and b-Ga2O3 are considered to be the most promising for DUV optoelectronic device application. Among them, ZnMgO has several advantages: large band gap tunability within 3.3-7.8 eV, large exciton binding energy (>60 meV for both binary constituents) at room temperature, material nontoxicity and abundance. However, since ZnO has hexagonal wurtzite (wz) crystal structure, and MgO has the cubic rock-salt (rs) structure, they do not show a complete solid solubility to grow ZnMgO alloy. As a result, it is difficult to achieve either wz- or rs-ZnMgO epitaxial layers exhibiting bandgap energy between 4.5-5.5 eV.
In a seminar, recent technological advances in epitaxial growing of ZnMgO will be presented, illustrating the structural and optical properties of the novel ternary alloys of ZnMgO. In particular, characteristic X-ray diffractograms (XRD), transmission/scanning electron micrographs (TEM/SEM) will be shown. Several useful optical characterization techniques (such as absorption, photoluminescense, ellipsometry) will be discussed, with a particular emphasis on a very sensitive modulation spectroscopy, enabling the investigation of fine bandstructure. Furthermore, advanced bandgap energy determination technique will be demonstrated.