Lateral oxidation kinetics of AlAsSb and related alloys lattice matched to InP

The lateral oxidation kinetics of AlAs0.56Sb0.44 on InP substrates have been investigated to understand the antimony segregation process during oxidation. Oxidation layers were grown between GaAsSb buffer and cap layers on InP substrates by molecular beam epitaxy. Oxidation temperatures between 325 and 500 degreesC were investigated for AlAsSb layer thicknesses between 100 and 2000 Angstrom. At low oxidation temperatures (T-ox less than or equal to 400 degreesC), the process is reaction limited with a linear dependence of oxidation depth on time. At intermediate oxidation temperatures (400 < T-ox < 450 degreesC), the oxidation process becomes diffusion limited. At high oxidation temperatures, the oxidation process is termed self-limiting since at 500 degreesC the process stops entirely after oxidation times on the order of 5 min and distances of 40 mum. It is shown that the antimony float layer lags the oxidation front by a temperature-dependent distance, which suggests that the antimony may change the structure of the oxide at the front and cause self-limiting behavior. The oxidation kinetics of AlxGa1-xAsSb and AlxIn1-xAsSb have also been investigated. Antimony segregation is not suppressed during oxidation of Ga-containing layers and AlInAsSb quaternary alloys do not oxidize laterally at measurable rates in the range 400-525 degreesC. SiNx cap layers deposited after growth and before oxidation do not affect the Sb segregation or oxidation rate, but do smooth the cap surface by preventing uneven Sb metal segregation to the cap/oxide interface. (C) 2001 American Institute of Physics.