Capacitance transients caused by capture and emission of electrons from buried metal disks are investigated. A single layer of tungsten disks, arranged in a square lattice, is introduced into GaAs by epitaxial overgrowth and a depleted layer is formed around the disks due to the metal–semiconductor Schottky barrier. The number of captured electrons on each disk is measured by the capacitance associated with the width of the depletion layer, whereas the capacitance transients reflect the changes in the number of excess electrons on the disks. By investigating the emission time constants for varying numbers of electrons in excess on the disks, the Coulomb effect is studied. In combination with a temperature-dependent capture, a Coulomb charging energy of only 4 meV is shown to shift the measured activation energies erroneously by hundreds of meV. © 1998 American Institute of Physics.