Sn and Te doping of molecular beam epitaxial GaAs using a SnTe source

Secondary ion mass spectroscopy and free electron concentration measurements have been used to study the incorporation of Sn and Te in MBE GaAs when SnTe is used as the source of these impurities. The probability of incorporation of Sn and Te approaches unity for substrate temperatures (TS )≲550 °C and decreases to less than 0.1 for TS ≳600 °C. This decrease is attributed to desorption of SnTe from the GaAs surface. A SnTe ’’pair’’ incorporation mechanism is proposed which dominates over the entire substrate temperature range studied. However, dissociation of SnTe molecules on the GaAs surface, with subsequent surface accumulation of Sn and Te, becomes non-negligible for TS ≳580 °C. A model is presented which explains these as well as other features of the experimental data.