Orientation dependence of oxygen adsorption on a cylindrical GaAs sample: I. Auger measurements

Abstract The orientation dependence of oxygen adsorption has been investigated by AES on the surface of a cylindrically shaped GaAs single crystal with [1110] being its axis. It thus exposes the main low index orientations (001), (111)Ga, (110), and (111)As, as well as all their vicinal surfaces and intermediate orientations on its surface. It is shown that it is possible to prepare all these orientations simultaneously and with reasonable quality by ion bombardment and annealing (IBA). The orientation dependence of the amount of adsorbed oxygen in the range (001)(111)Ga(110)(111)As can be understood in terms of different sticking coefficients on the different types of terrace site and of enhanced adsorption on edge-adjacent sites. These edge-adjacent sites show saturation at about 4 × 10 5 L. Starting from (110) towards (111)Ga, at first, steps one atomic layer high are found, changing to a height of two layers when approaching (331). This behaviour can be understood in terms of the known relaxation on (110). A deep minimum in the amount of adsorbed oxygen between (111)As and (001) is interpreted to be due to an As stabilized low sticking coefficient phase between (112) and (113). Early saturation (at∼10 5 L) on (001) and (111)As is consistent with the fact that these surfaces usually do not reach their room temperature equilibrium phase upon preparation by IBA. Sudden and accidental oxygen induced composition changes towards As-richer substrate compositions further confirm this.