Arsenic reflection from GaAs and AlGaAs surfaces during molecular‐beam epitaxy

An ion gauge with a direct line‐of‐sight view of the substrate can be used to monitor the reflected pressure of the group V species at all stages in the molecular‐beam epitaxial growth sequence. During growth of GaAs on rotating substrates, periodic oscillations in the pressure signal are observed when As2 is used for surface stabilization, but not with As4. These oscillations can be correlated to arrival of reflected As2 from the reconstructed surface of GaAs. Changes in oscillation amplitude as the substrate temperature is varied, or the arsenic flux is changed, are found to correspond with the onset of different surface reconstructions. Additionally, abrupt changes in the pressure and reflection mass spectrometry signals, which occur on initiating epitaxial deposition, are quantifiably proportional to relative growth rates. Thus, following an appropriate calibration, such measurements can be used for both growth rate and alloy composition estimation during normal epitaxial deposition sequences.