A study of the compositional changes in chemically etched, Ar ion bombarded and reactive ion etched GaAs(100) surfaces by means of ARXPS and LEISS

The effects of chemical etching, noble gas ion bombardment and reactive ion etching on GaAs(100) surfaces was investigated by angle resolved X-ray photoelectron spectroscopy (ARXPS) and low energy ion scattering spectroscopy (LEISS). The results show that at the “as received” GaAs surface, Ga oxide is the major component, resulting in a Ga concentration slightly higher than As. Chemical cleaning by hydrochloric acid (at a HCl(conc.) to H2O ratio of 1:1) followed by solvent washing efficiently removed the oxide layer, however, ARXPS showed that strong As enrichment occurs at the cleaned GaAs surface. Ion bombardment was carried out using 3 keV Ar ions with a beam current density of 1 μA cm−2 for a period of 50 min. XPS results show that at steady state the ion bombarded GaAs surface is depleted in As (AsGa ≈ 0.8), but ARXPS indicates an As increase at the very surface. This is further confirmed by Ne+ LEISS analysis, which shows in the top layer the As concentration is increased by 50% after ion bombardment. The results indicate that bombardment induced compositional changes in this surface are due to Gibssian segregation. The results of reactive ion etching in a 200 W Freon 12 plasma for a period of 5 min at 60 mTorr, showed that this apparently low damage process also produces significant compositional changes in the surface. The report illustrates the benefits of using complementary surface analytical techniques in such studies.