Semiconductor impurity parameter determination from Schottky junction thermal admittance spectroscopy

The problem of interpretation of thermal admittance spectroscopy data for s emiconductor impurity parameter extraction is considered. Traditional analy sis predicts that the Arrhenius plot for conductance peak temperatures is a straight line with the slope proportional to impurity activation energy an d the intercept determining its capture cross section. Using a general mode l of the Schottky junction admittance we show that conductance peak positio ns strongly depend on the impurity bulk occupation number and potential dis tribution in the space-charge region, and, as a result, the Arrhenius plot is nonlinear for some semiconductor parameters and experimental conditions, in particular for relatively shallow impurities. In this case, the traditi onal linear approximation of the Arrhenius plot yields inaccurate values of activation energy and capture cross section. We propose a more accurate pr ocedure for admittance spectroscopy data analysis involving least-squares f itting using the general and the small-signal models of the junction admitt ance. Although much more computationally intensive, the general model is sh own to provide a better fit to the data at low temperatures, where the smal l-signal approximation is invalid. This approach is applied for an example admittance data and yields a better fit of the theoretical curve to the dat a and an improved value of activation energy for the nitrogen donor in 6H-S iC. (C) 2001 American Institute of Physics.