Determination of Schottky-barrier with the help of measuring the activation energy

The main benefit of determination of Schottky-barrier with the help of measuring the activation energy is that we do not need any assumption of electrically active area. Particularly, this feature is crucial in the investigation of unusual or novel metal-semiconductor interfaces as we are not aware of the true value of the contacting area.

Activation-Energy Measurement:

If the surfaces are incompletely reacted or cleaned poorly then there will be only a little fraction of the geometric area in the electrically area. On the other side, a strong metallurgical reaction could provide rough nonplanar interface of metal-semiconductor with an electrically active area which is greater than the obvious geometric area.

The electrically active area, we get


where       is believed to be activation energy. For a limited temperature around the room temperature, the value of A** and F_bn are necessarily independent of temperature.

Therefore, for a fixed forward bias V_F the slope of a plot of In(I_F/T²) versus 1/T provides the barrier height F_bn and the ordinate intercept at 1/T = 0 gives the multiplicative result
of the electrically active area A and the effective Richardson constant A**.

To show the importance of the method of activation-energy in the investigation of interfacial metallurgical reactions, Fig. provided below gives the plots of activation-energy of the saturation current in Al-n-Si contracts of different heights of barrier, easily formed by annealing at different temperature.

The slopes of the plots depict an almost linear increase of effective Schottky barrier height from 0.71 to 0.81 V for annealing temperature between range of 450o C and 650o C.
The C-V and I-V measurements also provide confirmation for these observations.
Also, supposedly when the Al-Si eutectic temperature (= 580°C) is achieved, the genuine metallurgical nature of the interface of metal-semiconductor must be modified considerably.
Determining the ordinary intercepts from the plots represented in the fig. show that the electrically active area enhances by factor of two, when the temperature of annealing exceeds the temperature of Al-Si eutectic-temperature.