Evaluation of SIMOX substrates using photoconductive frequency resolved spectroscopy
In this thesis the application of Photoconductive Frequency Resolved Spectroscopy
(PCFRS) to determine excess carrier lifetime distributions and carrier recombination
kinetics in non-trivial semiconductor systems is described.
The excess carrier lifetime, as well as being of direct relevance to device
performance, is also a critical parameter in determining the quality of the
semiconductor system as it can provide information on the electrical activity of
defects present in the material. The theory of this technique is developed beyond the
current state-of-the-art and is applied in particular to the assessment of SIMOX
material, where other more conventional techniques have proved unsuitable.
A model to interpret the PCFRS response for carrier lifetime distributions, under
different injection conditions, is developed and, for the first time, the effect of
trapping is considered. We demonstrate how temperature dependent PCFRS can be
used to obtain the major trap parameters. This analysis is then used to evaluate trap
activation energies for a range of developmental SIMOX material produced both at
Surrey and commercially.
Our PCFRS results reveal that the SIMOX layers have a higher density of defects - as
compared to standard device quality silicon substrates. Characteristic parameters of
the dominant traps in these materials have been obtained from Arrhenius plots of the
lifetime distributions. The defects found in these SIMOX layers are shown to be
related to the high temperature anneal stage of the material production.