The use of an Arrhenius plot of the temperature dependent current-voltage at some appropriate voltage leads to a temperature and voltage dependent activation energy, which is shown to be identical to the average energy carried by the electrons in flowing between the contacts separated by a quantum well structure. An optimal temperature range is limited by the highest temperature the system can tolerate without deleterious effects. The effective barrier height determined in a limited voltage rangeV⩽2(E1−Ef)/eis equal to the ground state energyE1, of the quantum well structure. ©1997 American Institute of Physics.