Study of the chemical and morphological evolution of the GaAs surface after high fluence focused ion beam exposure

The impact of 50 keV focused Ga+ ion bombardment on semi-insulating GaAs has been investigated at various ion fluences in the range of 6.25 x 10(10)-1.25 x 10(17) ions/cm(2). As a result, the formation of spherical calotte shaped dots consisting of nearly pure gallium has been observed. The diameter of the calottes is in the range of 100 nm to more than 1 mum with an almost constant aspect ratio of about 0.4. The Ga dot formation promotes decomposition of the Ga-rich surface far below temperatures that have been reported for the thermal decomposition of undisturbed GaAs. The material decomposition occurs exclusively in the implanted regions, leading to micelle like structures on the irradiated surface. In this work, we present an experimental study of the morphological, chemical and electrical evolution of the GaAs surface under focused ion beam exposure by in situ FIB-secondary electron microscopy combined with atomic force microscopy, Auger electron spectroscopy, optical microscopy, and electrical measurements. (C) 2003 Elsevier B.V. All rights reserved.