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 241Am radionuclide source detected by the structures are also reported.