Temperature dependent barrier characteristics of CrNiCo alloy Schottky contacts on n-type molecular-beam epitaxy GaAs

Abstract

The current–voltage (I–V) characteristics of CrNiCo alloy Schottky contacts on a molecular-beam epitaxy n-GaAs substrate have been measured over the temperature range of 130–330 K and have been interpreted based on the assumption of a Gaussian distribution of barrier heights due to barrier height inhomogeneities that prevail at the interface. It is shown that the occurrence of Gaussian distribution of then barrier heights is responsible for the decrease of the apparent barrier height Φb0, increase of the ideality factor n and nonlinearity in the activation energy plot at low temperatures. A Φb0 vs 1/T plot was drawn to obtain evidence of a Gaussian distribution of the barrier heights, and values of Φ̄b0(T=0)=1.02 eV and σ0=0.105 V for the mean barrier height and zero-bias standard deviation, respectively, have been obtained from this plot. Thus, a modified ln(I0/T2)−q2σ02/2k2T2 vs 1/T plot gives Φ̄b0(T=0) and A* as 1.02 eV and 5.13 A/cm2 K2, respectively, without using the temperature coefficient of the barrier height. It has been concluded that the temperature dependent I–V characteristics of the device can be successfully explained on the basis of a thermionic emission mechanism with Gaussian distribution of the barrier heights. Furthermore, a value of −0.305 meV/K for the temperature coefficient of the flat band barrier height has been obtained; this value for n-GaAs is in very close agreement with values in the literature.