Effects of an Ion Bombardment on the Characteristics of a Metal/n-GaAs Tunnel Contact

Gallium arsenide surfaces have been submitted to low-energy ion bombardment. Metal/n-GaAs tunnel contacts realized on the surfaces prepared in this manner present features which depend greatly on the ion energy. At very low energy (50 eV) gas ions provide a ``cleaning'' of the interface and yield tunnel characteristics which are essentially identical to those of a vacuum-cleaved analogous contact. This technique may be used to define the origin of tunneling anomalies. Higher-energy bombardments (100–150 eV) lead to strong changes of the tunnel properties which can be summarized as a large resistance increase in spite of a strong barrier lowering and the appearance of inelastic processes. A model based on the creation of structural defects accounts qualitatively for all of the observed phenomena. Tunneling represents, therefore, a promising technique in the study of very-low-energy ion bombardments.