An important application of photoemission spectromicroscopy would be to measure heterostructures
and semiconductor devices in cross section to directly determine band offsets and band bending.We
present here studies of p-n GaAs homojunctions and Al/GaAs Schottky junctions fabricated by
molecular-beam epitaxy. Our results suggest that a minimum experimental uncertainty of about 0.15
eV will effect band offset determination. In general, useful quantitative information on the junction
electrostatics can be obtained provided that the experimental data are analyzed to substract the
diffuse photon background and take into account the intensity profile of the photon spot.
