Surface‐stoichiometry dependence of As₂ desorption and As₄ ‘‘reflection’’ from GaAs(001)

Using real‐time reflection mass spectrometry, we have measured the temperature dependence of As₂ desorption and As₄ ‘‘reflection’’ from a GaAs(001) surface. The measurements agree well with the second‐order flux‐balance equation expected to govern surface stoichiometry, and determine its rate constant. Using that rate constant, the equation associates physically reasonable surface stoichiometries with the various well‐known GaAs(001) surface reconstructions, and is strikingly consistent with measurements of the times for surface reconstruction changes in the absence of an As ambient.