Oxygen doping of c-plane GaN by metalorganic chemical vapor deposition

Oxygen doping of c-plane GaN was investigated by metalorganic chemical vapor deposition (MOCVD), using O-2 as the oxygen precursor. The oxygen incorporation into GaN was strongly affected by the surface orientation of the GaN film. At an O-2 partial pressure of 10 Pa, growth on a smooth (0001) GaN surface resulted in an oxygen concentration of 8 x 10(16) cm(-3). However, the oxygen incorporation increased drastically to concentrations up to 3 x 10(19) cm(-3), when the growth was performed on rough surfaces containing other crystal planes than (0001) GaN. Such surfaces include (0001) GaN with hexagonal pits, or the hexagonal islands formed during the initial stage of growth of GaN films on sapphire substrate. Furthermore, above a certain critical O-2 partial pressure, which depended on the growth temperature, oxygen itself caused a perturbation of the smooth GaN growth on (0001) surfaces, leading to the formation of hexagonal pits during growth. The highest oxygen concentration attained during smooth growth was 3.5 x 10(17) cm(-3). The results imply, that oxygen is not a suitable dopant for the growth of uniform n(+) (0001) GaN layers. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.