THE STUDY OF RIPPLE FORMATION AND DEGRADATION OF DEPTH RESOLUTION IN GAAS AND ALXGA1-XAS STRUCTURES

The present work investigates the characteristics of ripple formation in AlxGa1-xAs samples under oxygen irradiation. The wavelength and the amplitude of the ripples have been determined under different conditi ons and are examined within the scope of two existing theoretical mode ls: the model of Bradley and Harper [1] and the local incorporation mo del [12]. It is shown that oxygen bombardment of AlxGa1-xAs (with 0 le ss than or equal to x less than or equal to 0.56) structures with an i mpact energy of 8 keV at 37 degrees always produces ripples. Both the wavelength as well as the growth rate of the ripples are affected by t he stoichiometric composition of the sample analyzed, the temperature, and the oxygen pressure near the sample. The work shows that the loca l incorporation mechanism contributes to the ripple growth and explain s correctly the increase in ripple amplitude when introducing oxygen g as near the sample. Moreover, it also accounts for the material depend ence and the strong reduction in ripple growth rate at the highest pre ssures. Neither of the two models can explain the dependence of the ri pple formation as a function of the temperature. (C) 1997 Elsevier Sci ence B.V.