  Free surfaces of semiconductors respond to light by varying their surface
voltage (surface band bending). This surface photovoltage may be easily
detected using a Kelvin probe. Modeling the transient temporal behavior of the
surface photovoltage after the light is turned off may serve as a means to
characterize several key electronic properties of the semiconductor, which are
of fundamental importance in numerous electronic device applications, such as
transistors and solar cells. In this paper, we develop a model for this
temporal behavior and use it to characterize layers and nanowires of several
semiconductors. Our results suggest that what has previously been considered to
be a logarithmic decay is only approximately so. Due to the known limited
frequency bandwidth of the Kelvin probe method, most previous
Kelvin-probe-based methods have been limited to slow responding semiconductors.
The model we propose extends this range of applicability.
