Surface states studies in semiconductors by photothermal deflection spectroscopy

Abstract

A method based on the analysis of both the amplitude and phase of the photothermal deflection spectroscopy signal which enables one to locate surface states on the front or rear surface of semiconductor wafers and to measure their absorption. The procedure also allows the determination of the sample thermal conductivity

Defect density measurements of low temperature grown molecular beam epitaxial GaAs by photothermal deflection spectroscopy

“…Below the band-gap energy, the phase lag becomes smaller for smaller photon energies because the center of absorption moves to the front surface where the absorption is dominated by the MBE layer. Similar phase motion has been observed previously by Zammit et al 18,19 The PDS phase spectrum for the 585°C sample ͑ob- tained at a chopping frequency fϭ13 Hz͒ also shows a similar phase shift just below the band gap. However, the phase lag becomes larger for smaller photon energies.…”

The development of a novel technique to evaluate theCR-39 track response to alpha particles

“…The dip can be interpreted as occurring because of extra heat absorption in the damaged zones by α -particles of the CR-39 and lowering of the deflection in the lock-in amplifier. The PDS signal amplitude depends on the sample light absorption while the signal phase depends on the localization of the effective "center" of absorption within the sample [16].…”

Photothermal beam deflection technique for non-destructive evaluation of thin film photovoltaic cells

“…A one-dimensional model of heat flow in the cell resulting from the absorbed light energy was put forth by Rosencwaig et al [32] for measuring the signal generated in photoacoustic technique. Later in 1990, U Zammit et al [33] developed a 1-D theoretical model for analysis of photothermal deflection signal amplitude and phase. According to this theory any light absorbed by the solid is converted, in part or whole, into heat by non-radiative deexcitation processes within the solid.…”

“…Theoretical model for photothermal analysis of semiconductor put forth by U Zammit et al [33] does not include non-radiative recombination and surface recombination processes taking place in the semiconductors and the model given by Fournier et al [34] does not suit the three layer sample geometry with fluid, sample and backing layer; hence the present model was extended to suit the transverse photothermal beam deflection technique with three-layer sample geometry, assuming the sample to be a semiconductor thin film. Accuracy of the measurement technique can be improved by further refinement of the theoretical model.…”