High power terahertz photoconductive antenna with hybridized contact electrodes

In a photoconductive antenna, the photocurrents and antenna properties are greatly influenced by the type of electrodes, either Ohmic or Schottky contact electrodes fabricated on semi-insulating GaAs. In our theoretical model, Schottky contact, having a small chemical potential gradient, discourages electromigration of contact metal atoms whereas Ohmic contact tends to induce stronger photocurrents, generating a terahertz beam more efficiently for a given bias field. However, with actual electrodes fabricated on a semi-insulating GaAs substrate, the contact exhibits either Ohmic-dominant or Schottky-dominant hybridized behavior, instead of having either pure Ohmic or pure Schottky behavior. Interestingly, hybridized Schottky contacts suppress electromigration of contact metal atoms into the substrate and also improves the efficiency of terahertz beam generation, taking both advantages of Schottky and Ohmic contacts. Furthermore, due in part to the suppressed electromigration, the photoconductive antenna with Schottky electrodes becomes more durable and tolerate a high bias voltage that enables a more intense terahertz beam.