Indium incorporation during the growth of (100)Si by molecular beam epitaxy: Surface segregation and reconstruction

The In incorporation probability σIn in (100) Si grown by molecular beam epitaxy was found, using secondary ion mass spectrometry (SIMS), to decrease from essentially unity at film growth temperatures Ts of ∼500 °C to <10−4 at 840 °C. SIMS depth profiles of both uniformly doped and modulation-doped samples showed evidence of strong surface segregation with the amount of profile broadening directly related to σIn(Ts). A combination of in situ electron diffraction and Auger electron spectroscopy was used to show that the surface segregation rate was sufficient over a wide range in Ts and In to Si flux ratios to cause the initial (2×1)-(100) Si surface reconstruction to transform to (3×4) due to the formation of an ordered In surface layer. The In surface coverage in the (3×4) state was ∼0.05–0.1 monolayer even though the bulk In concentration was ≤2×1017 cm3. The (2×1) to (3×4) surface phase transition was reversible by either terminating film growth and reevaporating the excess surface In or terminating the In flux while continuing Si film growth.