The deposition of gallium nitride and aluminium nitride thin films on GaAs(
100) substrates by chemical beam epitaxy is reported. In-situ dynamic optic
al reflectivity has been used to compare growth rates of the nitride layers
as a function of substrate temperature with their arsenide analogues. The
relative growth efficiency of gallium nitride/gallium arsenide from triethy
l gallium was found to be in the range 75-85%. The growth temperature for g
allium nitride extends to higher temperatures, compared with gallium arseni
de, probably due to lower evaporation rates of Ga bound to the nitride surf
ace. At the same beam equivalent pressure, the growth rate of aluminium nit
ride from ethyldimethyl aluminium alane is approximately one-third of that
for gallium nitride from triethyl gallium. Atomic force microscopy reveals
that the gallium nitride surface formed at 500 degrees C is facetted, where
as an aluminium nitride surface deposited at 400 degrees C exhibits a round
ed columnar type growth habit. Reflection anisotropy spectra indicate that
atomic nitrogen readily reacts with the GaAs(100)-c(4 x 4) As stabilized su
rface at temperatures as low as 400 degrees C but without the gross facetti
ng that has been observed at higher temperatures. (C) 1999 Elsevier Science
S.A. All rights reserved.