PROPERTIES OF SI DONORS AND PERSISTENT PHOTOCONDUCTIVITY IN ALGAN

The behavior of Si donors was studied in AlxGa1-xN films with composit ion 0 < x < 0.6. It is shown that the Si donors ionization energy incr eases from 18 meV for 0 < x < 0.1 to about 50 meV for x = 0.4 and does not exceed 90 meV for x = 0.6. Increase in Al composition is also acc ompanied by the growth of the density of defects with energy levels de eper than Si. Combined action of the two above effects leads to increa sed difficulty in n-type doping of AlGaN films with higher Al mole fra ctions. Persistent photoconductivity (PPC) is shown to be a characteri stic feature of AlGaN samples of all compositions. It is shown that PP C in AlGaN is related to the presence of centers with a relatively hig h (0.1-0.2 eV) barrier for capture of electrons. In GaN and AlGaN with x < 0.1 such centers are not associated with Si donors per se. (C) 19 98 Elsevier Science Ltd. All rights reserved.