Reverse I-V characteristics of Au/semi-insulating GaAs(100)

The reverse I-V characteristics of the Au/semi-insulating (SI)-GaAs(100) contact structure have been studied in the temperature range 240-300 K. The temperature dependence of the resistance determined from the low bias (0-15 V) linear portion of the I-V curves gives a Fermi-level position for the bulk GaAs 0.68+/-0.05 eV below the conduction band, in good agreement with that determined from other techniques, indicating that the reverse current transport in this regime is predominantly determined by the bulk resistance of the Si-GaAs. At higher reverse biases a current limitation establishes which is explained in terms of thermionic and thermionic field emission across the Au/SI-GaAs Schottky-like barrier. The electric fields that occur at the interface cause a larger than expected saturated emission current due to the barrier lowering effect and because the effective Richardson constant increases by about two orders of magnitude as electrons are transferred into the L band minima of the GaAs. The onset of the GUM effect also explains the saturation of the reverse current for applied biases greater than 50 V where the electric field close to the interface self limits through the faster EL2(+) electron capture from the L band. (C) 1997 Elsevier Science Ltd.