Investigation of rapid thermally annealed GaP(001) surfaces in vacuum

Morphology of rapid thermally annealed GaP(001) surfaces has been investigated using spectroscopic ellipsometry (SE), optical microscopy, ex situ atomic force microscopy, electron probe microanalysis (EPMA) and X‐ray photoelectron spectroscopy (XPS). The samples were annealed in vacuum for t = 2 s at temperatures T = 20–900 °C. The SE, optical microscopy and XPS spectra suggest that thermal annealing causes little influence on the GaP surface at T ≤ 600 °C; however, micro‐ and macroscopic roughening occur at T > 600 °C and T ≥ 750 °C, respectively, with a generation of Ga droplets at T ≥ 750 °C. The presence of the Ga droplets is confirmed by the EPMA measurements. The droplet density can be expressed as N_Ga ∝ exp (E_a/k_BT) with an activation energy of E_a ～ 2.3 eV. The XPS data indicate the change in the surface oxide composition from the native oxide to the Ga oxide (Ga₂O₃ and Ga₂O) after annealing at T ≥ 750 °C. Possible annealing‐induced degradation steps are proposed to provide as complete a picture as possible. Copyright © 2010 John Wiley & Sons, Ltd.