Homoepitaxial AlN thin films deposited on m-plane ( 1 1 ̄ 00) AlN substrates by metalorganic chemical vapor deposition
AlN homoepitaxial films were grown by metalorganic chemical vapor deposition on chemo-mechanically polished ( 1 1 ̄ 00)-oriented single crystalline AlN substrates. The dependence of the surface morphology, structural quality, and unintentional impurity concentrations on the growth temperature was studied in order to determine the most appropriate growth conditions for high quality ( 1 1 ̄ 00) AlN epitaxial layers. Optically smooth surfaces (RMS roughness of 0.4 nm) and high crystalline quality, as demonstrated by the presence of FWHM values for ( 10 1 ̄ 0) rocking curves along [ 0001] of less than 25 arc.sec, were achieved for films grown above 1350 °C. Furthermore, sharp and intense near band edge luminescence was observed in these high quality films. A reduction in unintentional oxygen impurity levels was seen with an increase in growth temperature. These high crystalline quality films are suitable for device applications and hold great potential for providing an ideal platform for deep UV emitters with high Al content AlGaN without polarization related effects.