BEEM study of electron tunnelling across single AlAs barriers

Ballistic electron emission microscopy (BEEM) has been used to study the electron transport across single potential barriers. The system used was a Au/GaAs/AlAs/GaAs mixed heterostructure, in which the Au forms a Schottky contact to the GaAs and the AlAs layer acts as a buried potential barrier to the electron conduction. The barrier thickness has been changed in a wide range from 0 to 300Åfor which tunnelling probabilities were calculated theoretically, compared with the BEEM data and found to be in good agreement with the measured lowest thresholds. The suitability of the ‘square law’ as a fitting theory in dealing with this tunnelling situation was examined and some modification was found necessary.