Use of finite gate widths in multipoint correlation methods for DLTS characterization of semiconductors

Abstract

One of the latest proposals for the DLTS analysis of transients in Schottky barriers, pn junctions or MOS structures is that from Dmowski's methods. By using a multipoint correlation function, selectivity can be improved at the cost of decreasing sensitivity. When used in a computerized system, such correlation signals are quite sensitive to noise, leaving a DLTS signal plot in which the peaks are frequently difficult to recognize. Thus in noisy media it is better to calculate DLTS signals by using finite gate widths in the processing of experimental data, so as to improve the signal to noise ratio (S/N). In order to interpret the results, calculations have been made using different gate widths, for a correlation function with n = 5 sampling points at times i among which the ratio r = t i / t i −1 = 2 is kept constant for i = 2, 3, 4, 5. Results for the signal-to-noise ratio, sensitivity and selectivity are presented for three special cases with distinct relative δt. The convenience of placing t i at some specific position within δt in order to improve sensitivity, selectivity or S N ratio is mentioned.