HYDROGEN INDUCED STRUCTURE CHANGES OF GAAS(1 0 0) SURFACES

The interaction of hydrogen with GaAs(100) surfaces has been studied at room temperature by means of high-resolution electron energy-loss spectroscopy (HREELS), low-energy electron-diffraction (LEED), and Auger electron spectroscopy (AES). Sample cleaning by Ne+ ion bombardment (500 eV) and annealing resulted (with increasing temperatures) in "1 x 1", 1 x 6, 4 x 1, 4 x 6 and c(8 x 2) LEED structures. As a function of hydrogen exposure, the intensity ratio of the stretching vibrations (As-H/Ga-H) is shown to be characteristic for the specific reconstructed surface. In particular the arsenic hydride concentration gradually decreased in all cases. In addition, an initial weakening of the fractional order LEED spots occurred with increasing hydrogen exposures. Finally, a strong 1 x 2 structure was observed independent of the reconstruction we started with. Simultaneously, a shift of the energetic position of the Ga-H stretching vibration occurred.