CRITICAL ANALYSIS OF WEIGHTING FUNCTIONS FOR THE DEEP-LEVEL TRANSIENTSPECTROSCOPY OF SEMICONDUCTORS

More than 20 weighting functions proposed for DLTS are critically comp ared. It is shown that the variety of DLTS peak widths of different we ighting functions was primarily due to the variety of shapes of the hi gh-temperature side of the peak. A refinement of the classification sc heme of the weighting functions is proposed. It is shown that the high -temperature side of the DLTS peak can be made independent of the weig hting function, by considering the delay time td between the end of th e filling pulse and the beginning of the weighting function as an inte gral part of each weighting function. An optimum delay time (specific for each weighting function) is obtained by maximizing the figure of m erit defined as the signal-to-noise ratio of the correlator divided by the DLTS peak width. Using the concept of optimum delay time, the fun ctions can be classified into several groups according to their select ivity. The functions from one group differ only by their sensitivity, making it easy to select the functions with the best signal-to-noise r atios. In the second part of the paper, several misunderstandings conc erning exponential correlators and double boxcars that frequently appe ar in the literature are revealed.