2-LAYER MODEL FOR PHOTOMODULATED THERMOREFLECTANCE OF SEMICONDUCTOR WAFERS

A complete theoretical analysis of the laser photomodulated thermorefl ectance signal from a two-layer semiconducting wafer is presented. It is shown that the electronic and thermal properties of a thin surface layer may be determined by using the measured induced photothermal sig nal. Several numerical simulations are performed in order to study the influence of various electronic, optical and thermal parameters of th e two-layer sample on the photomodulated thermoreflectance signal. The influence of the upper layer as well as the influence of the substrat e on the signal are also discussed and parameter regimes are identifie d, where the characterization of the thin overlayer may be possible us ing this technique. (C) 1996 American Institute of Physics.