Photoacoustic investigation of transport in semiconductors: Theoretical and experimental study of a Ge single crystal

Abstract

Photoacoustic (PA) heat-transmission measurements were used to study transport in a nearly intrinsic Ge single crystal. A theoretical model was developed which quantitatively describes excess carrier and thermal-wave space distributions, within the semiconductor under monochromatic cw modulated excitation. The PA heat-transmission, reflection, and photothermal-beam-deflection signals can be calculated using this model. It is shown that the frequency characteristic of the measurement system can be eliminated using measurements on different thicknesses of the same sample. It is also shown that both the normalized phase and amplitude spectra, as a function of the modulation frequency, can be used to determine the values of the thermal diffusivity, the excess-carrier lifetime, and the surface recombination velocity.