where [I.sub.0] is the saturation current; S is metal-semiconductor contact area; A is Richardson constant; k is Boltzmann constant.
The Richardson constant is usually assumed to be 120 A [cm.sup.-2] [K.sup.-2], but in  it is indicated that the experimental values of A may not coincide with the given value.
where [E.sub.m] = [square root of ((2q[N.sub.D]/[[epsilon]'.sub.S])([V.sub.n] + [[phi].sub.B] + (kT/q) + V))], [A.sup.*] = 9.6 A/k-[cm.sup.2], A [approximately equal to] 8 x [10.sup.-4] [cm.sup.2], T = 300 K, q = 1.6 x [10.sup.-19] C, k = 1.38 x [10.sup.-23] J/K, [[phi].sub.B] = 0.83 eV, [N.sub.d] = 8 x [10.sup.16] [cm.sup.-3], 4 = 10.8, [[epsilon].sub.S] = 12.9, [V.sub.n] = 0.05 V, and V = 0 V to 5 V are the maximal electric field, the Richardson constant
, contact area, absolute temperature, unit electronic charge, Boltzmann constant, barrier height, doping concentration, permittivity of GaAs near the Pd, permittivity of GaAs, Fermi potential from conduction-band edge, and applied voltage, respectively.