Role of contacts in metal/semi-insulating GaAs/metal structures: Symmetrical geometry

Comparative study of AuGeNi, Pt, Nd and Gd contacts on semi-insulating (SI) GaAs with respect to the backside quasi-ohmic AuGeNi contact in symmetrical geometry is investigated. Fabricated diode structures are characterized by the current- and capacitance-voltage dependencies. Each of contacts gives an original set of characteristics and current lower that corresponding to the ohmic, bulk limited transport in the initial, low bias (<0.02 V) region. Observed increase of UV photosensitivity in the structure with Gd contact is explained by the formation of a heterojunction Au/Gd2O3/SI-GaAs.