Possibility of two-step As-desorption from (001) InP using surface photoabsorption

We present an in situ investigation of As-desorption from the (001) InP sur face using surface photoabsorption (SPA). At 470 degreesC, we observed that the SPA signals along [110] remained unchanged even after the AsH3 supply was turned off, while the SPA signal along [110] showed a sharp increase as reported previously. We also measured SPA spectra at several stable states and found that the surface after AsH3 was turned off could not reach that of an In-stabilized surface. We interpret these results in terms of As-de-s orption occurring possibily as a two-step process, in contrast to P-desorpt ion of a one step process.