Calibration of the arsenic mole fraction in MBE grown GaAsySb1-y and AlxGa1-xAsySb1-y (y < 0.2)

We present a systematic study mapping how the As incorporation into GaAsySb 1-y and AlxGa1-xAsySb1-y (y < 0.2) grown by molecular beam epitaxy under Sb overpressure varies under different growth conditions. GaAsSb epilayers we re grown on GaSb substrates with different As fluxes, growth rates, and sub strate temperatures. X-ray diffraction was used to determine the As mole fr action in the samples. The As mole fraction when growing GaAsSb in Sb overp ressure was found to (i) be much less sensitive to unwanted variations in t he Sb flux as compared to growing in Sb underpressure (i.e. with Sb/III Aux ratio less than unity), (ii) increase with increasing As flux, (iii) incre ase with increasing substrate temperature, and (iv) increase with decreasin g Ga flux. AlGaAsSb epilayers with different Al mole fractions were also gr own. No enhancement in the As incorporation due to Al was found for these g rowth conditions. (C) 2001 Elsevier Science B.V. All rights reserved.