Preferred orientation of AlN plates prepared by chemical vapour deposition of AlCl3 + NH3 system

Abstract

Aluminium nitride (AlN) plates about 1 mm thick (maximum) were prepared by chemical vapour deposition (CVD) at the maximum deposition rate of 430 nm s−1 using AlCl3, NH3 and H2 gases at deposition temperatures,Tdep, of 873–1473 K. The effects of deposition conditions on the preferred orientation, morphology and micro-structure were investigated. WhenTdep was less than 1073 K, the resulting CVD AlN plates contained some impurity chlorine and the aluminium content exceed the nitrogen content. WhenTdep exceeded 1173 K, no chlorine was detected, and the Al/N atomic ratio matched the stoichiometric value. The lattice parameters (a=0.311 nm,c=0.4979 nm) and density (3.26×103 kgm−3) were in agreement with values reported previously. The crystal planes oriented parallel to the substrates changed from (1 1 ¯2 0) to (1 0 ¯1 0) to (0001) with increasing total gas pressure (Ptot) and decreasingTdep. This tendency is discussed thermodynamically and is explained by the change of supersaturation in the gas phase.