Temperature-dependent behavior of low-temperature-grown GaAs nonalloyed ohmic contacts

A study of nonalloyed ohmic contact structures consisting of Au/Ti metallization deposited on a thin (3.5-5 nm) layer of low-temperature-grown GaAs (LTG:GaAs) on a thin (10 nm) layer of heavily doped n-type GaAs is summarized. We demonstrate that this Au/Ti:LTG:GaAs/n(+)GaAs contact structure has a stable specific contact resistance between 40 and 300 K, with measured contact resistance as low as 2x10(-6) Omega cm(2) at 40 K. Based on comparisons of the measured data with calculations using a uniformly doped Schottky model, we infer that the activation doping density in these structures is higher than 5x10(18) cm(-3), and that the surface potential barrier height is lower than 0.7 eV (midgap). The characteristic current-voltage curves of the nonalloyed contact show that tunneling is the primary conduction mechanism. (C) 2001 American Institute of Physics.