PROPERTIES AND APPLICATIONS OF MBE GROWN ALGAN

AlGaN epitaxial films have been grown on sapphire by plasma-induced mo lecular beam epitaxy (MBE) over the entire composition range from GaN to AlN. Structural and optical properties of the alloys have been inve stigated by X-ray diffraction (XRD), transmission electron and atomic force microscopy, Raman scattering, ellipsometry, optical transmission , and subgap absorption spectroscopy. Electron spin resonance has been used to study the dependence of intrinsic paramagnetic defects on Al mole fraction. N- and p-type doping with Si and Mg, respectively is fo und to become increasingly difficult with increasing Al content becaus e of a continuous shift of the donor and acceptor levels deeper into t he bandgap. Apart from the use of AlGaN as cladding layers in light em itting diodes, applications in MODFET transistors, solar blind photode tectors, surface acoustic wave devices and Bragg reflectors appear int eresting and will be discussed briefly. (C) 1997 Elsevier Science S.A.