Surface chemistry evolution during molecular beam epitaxy growth of InGaAs

1995 
Temperature‐programmed desorption (TPD) measurements are carried out in a molecular beam epitaxy (MBE) growth chamber on pseudomorphic GaAs/In0.22Ga0.78As(125 A)/GaAs single quantum wells in various stages of growth, using a line‐of‐sight mass spectrometer for quantitative desorption analysis. The presence of surface‐segregated indium is inferred from the appearance of a relatively low binding energy (Eb≊1.5 eV) peak in the indium TPD spectra. Integration of this TPD peak provides a quantitative measure of the surface‐indium population ΘIn. By incorporating the TPD experiment as a subroutine in the MBE growth program, systematic variations of growth parameters are effected and their influence on ΘIn established. Detailed composition profiles are calculated and found to be in excellent agreement with previous results [Nagle et al., J. Cryst. Growth 127, 550 (1993)]. We find that both the bottom (InGaAs on GaAs) and top (GaAs on InGaAs) interfaces are graded over as much as 10 monolayers, with the bottom in...
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