Schottky-Barrier Properties of Nearly-Ideal (n ≃1) Al Contacts on MBE- and Heat Cleaned-GaAs Surfaces

Abstract
Aluminum films were deposited in ultra-high vacuum onto heat-cleaned-surfaces as well as oxygen-free MBE surfaces of (100) GaAs to form Schottky barriers with and without intervening oxide layers. The measured ideality factor n was close to unity (n≃1.02∼1.10) irrespective of the oxide thickness t ox, indicating the transport being dominated by thermionic emission processes. In contrast, the barrier height decreased systematically from 0.89 eV to 0.67 eV, as t ox is reduced, suggesting the presence of negatively charged centers (≃1012/cm2) at GaAs/oxide interfaces.