A new kind of quasi-ohmic metallization in semi-insulating GaAs: Study of electrical characteristics

The present work describes current-voltage (I-V) characteristics of radiation detector structures based on semi-insulating (SI) GaAs obtained with new types of metallizations used to form quasi-ohmic contacts. Three different metals (In, Gd and Mg) having lower work function in comparison with the standard AuGeNi eutectic alloy, were used. These metals are expected to form a band bending at the M-S interface which should give rise to a blocking barrier for holes ("minority" carriers in SI GaAs). Such contacts, which could effectively replace standard alloyed N+ "ohmic" contact, show an unusual electrical charge transport as deduced from the measured I-V characteristics. Pulse-height spectra of Am-241 radionuclide source detected by the structures are also reported.