Low-frequency noise and current-voltage characteristics of Schottky barrier contacts in a wide temperature range

The low-frequency (1/f) noise and current-voltage characteristics of GaAs and Si Schottky barrier diodes are studied over a wide temperature range: 77-400 K. The peculiarities of temperature and current dependences of the spectral intensity (SI) of current fluctuations S-i(I,T) (a specific increase of the SI with decrease in temperature and a deviation from a quadratic dependence of the S-i-I-2 form) are explained adequately by the influence of a predominantly local barrier height lowering at a Schottky barrier contact (SBC), most likely at its periphery. The Gaussian barrier height distribution at SBCs does not explain these peculiarities. It is shown that the 1/f noise at SBCs approaches the "ideal" noise of the S-i-I-beta/f(alpha) form, where beta=2 and alpha=1, as the temperature increases. The explanation for the "low-temperature anomaly" in SBCs [an increase in the ideality factor n and a decrease in the measured (from a saturation current) barrier height Phi(bm) with decrease in temperature, a weak variation of their product Phi(bn)equivalent tonPhi(bm) in this case, and the character of the temperature dependence n(T) in the form of ncongruent to1+T-0/T ("T-0 effect")] is presented. This explanation is based on a fundamental property of real SBCs-the nonlinear bias dependence of the barrier height resulting in a growth of the ideality factor with a bias voltage (current) increase. The other necessary condition for revealing the "low-temperature anomaly" is the inclusion in theory of the fact that the n and Phi(bm) measurements are performed at the same current for all temperatures. An expression for the flatband barrier height Phi(bf) is derived. It takes into account the nonlinear bias dependence of the barrier height and the n(I) dependence which follows from it. On the basis of this expression the conditions are defined at which a simple approximation for Phi(bf) is valid: Phi(bf)congruent toPhi(bn)equivalent tonPhi(bm). (C) 2002 American Institute of Physics.