Ballistic electron emission spectroscopy (BEES) has been performed on a GaAs/Ga0.8Al0.2As/GaAs single-barrier structure at 77 and 7 K. The single-interface model widely used for such structures was found to be inadequate in describing the BEES second-derivative spectrum. A more complete model that incorporates electron-wave interference effects is shown to describe the data accurately and consistently over many spatial locations and samples. This model reproduces all measured features in the BEES second-derivative spectrum resulting from electron-wave interference. At 77 K (7 K) the conduction band offset for x=0.2 is determined to be 145 meV or Qc=0.58 (150 meV or Qc=0.60) in agreement with accepted values. © 1997 American Institute of Physics.