Effects of vacuum annealing on the electronic properties of cleaved GaAs

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Abstract
Low-energy electron diffraction, Auger electron spectroscopy and photoemission yield spectroscopy measurements have been performed on GaAs samples cleaved in ultra-high vacuum and subject to in situ isochronous anneals up to 850 degrees C. The properties of the cleaved (110) surface remain unchanged up to about 350 degrees C. Around this temperature, a dissociation occurs inducing a local reconstruction of the surface; at the same time, new states appear which may be attributed to Ga vacancies. Then, around 580 degrees C, the well known dissociation of GaAs sets in with formation of As2, and the Ga-Ga bonds which then form, determine the electronic properties of the sample. Evaporation of arsenic would become dominant around 650 degrees C. Beyond about 780 degrees C, the excess Ga coalesces into Ga-metal droplets and the GaAs substrate undergoes faceting.