Factors affecting the growth of aluminium nitride layers on sapphire by the reaction of nitrogen with aluminium monoselenide

Abstract

Aluminium nitride has been deposited on sapphire substrates by the reaction between aluminium monoselenide Al 2Se and nitrogen at temperatures in the range 1540–1600°C. The Al 2Se was generated in the reactor by the reaction of Al 2Se 3 and excess aluminium. The preparation of Al 2Se 3 is described. Three orientations of sapphire were used, 1 1 100, 1 2 10, and 1 1 02, and morphological quality of layers grown on each substrate orientation examined by diffractometry and SEM. Surface features arising from gas etching of the substrates by hydrogen and Al 2Se are described. It has been observed that there is direct reaction between sapphire and nitrogen gas at temperatures greater than 1200°C leading to slow etching (∼ 0.2 μm/h), roughening of the surface and partial replacement of Al 2O 3 by AIN. Small crystals (∼0.1mm) of AIN obtained by unwanted reaction between the Al 2Se source material and N 2 show the same morphology as flux-grown crystals of BeO, known to contain c-axis antiparallel twins, suggesting that similar c-axis twinning may be common in AIN.