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

Abstract

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 Si(I,T) (a specific increase of the SI with decrease in temperature and a deviation from a quadratic dependence of the Si–I2 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 Si–Iβ/fα form, where β=2 and α=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 φbm with decrease in temperature, a weak variation of their product φbn≡nφbm in this case, and the character of the temperature dependence n(T) in the form of n≅1+T0/T (“T0 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 φbm measurements are performed at the same current for all temperatures. An expression for the flatband barrier height φbf 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 φbf is valid: φbf≅φbn≡nφbm.