Electrical properties of Schottky diodes of Ti on highly doped GaAs

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Abstract
I-V and C-V characteristics of Schottky diodes prepared by Au/Pt/Ti evaporation and by Ti sputtering on GaAs substrates with electron concentrations of 1.5×1017, 4.5×1017, and 3.5×1018 cm−3 were measured as a function of temperature between 77 and 300 K. The ideality factor was found to follow the theory of thermionic field emission. Closer agreement with that theory was observed for evaporated and annealed diodes and for sputtered diodes than for evaporated, as-deposited devices. The sputtered diodes exhibited the best I-V characteristics with an ideality factor n=1.04 and a reverse current lower by more than two orders of magnitude than that of the evaporated devices at 300 K. This behavior was attributed to the presence of an interfacial oxide layer in the evaporated devices. Departure from the thermionic field emission theory was observed in devices with Nd≥4.5×1017 cm−3 at low forward bias and was attributed to current transport due to a mechanism of multistep recombination tunneling through defects.