INFLUENCE OF LAYER THICKNESS AND PRIMARY ION ON PROFILE BROADENING DURING SPUTTERING OF AL0.5GA0.5AS GAAS STRUCTURES/

Broadening of secondary ion mass spectrometry depth profiles for Al in Al0.5Ga0.5As/GaAs structures, where the layer thicknesses vary from t wo monolayers to 1000 angstrom, is investigated. The experiments were performed in the net primary energy range 1.8-13.2 keV with Ar-40+ ion s and Kr-84+ ions. The broadening is mainly determined by ballistic mi xing, and no dependence on the Al0.5Ga0.5As layer thickness is reveale d. Good agreement is found with a semi-empirical mixing model publishe d recently by Zalm and Vriezema and [Nucl. Instr. and Meth. B 67 (1992 ) 467] although a small contribution from surface roughness occurs. Th e surface roughness develops initially but saturates already after the first Al0.5Ga0.5As layer.