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A. Jariwala et al.
1 Introduction
The surface photovoltage spectroscopy (SPS) relies on the measurements of surface
photovoltage (SPV) phenomenon as a function of incident photon energy. It is a versatile, contactless, non-destructive characterization technique, which has been successfully employed extensively for characterization of various semiconductor materials
and devices. These include surfaces, thin films, bulk materials and nanostructures of
a variety of semiconductors materials and interfaces [1–6].
In early pioneering work, surface photovoltage (SPV) was used to study effects of
adsorbates on the surface potential (Vs) of Ge by Brattain and Bardeen in 1953 [7] and
subsequently by E. O. Johnson in 1957 [8]. Since then it has been used extensively
in the last seven decades in order to probe electronic and optical properties, such as
optical band gap, surface states, surface oxide thickness, minority carrier diffusion
length and their lifetimes for various materials systems. The SPS has also been
applied in case of quantum structures to determine the band-offsets [9–14]. The
major breakthrough in the timeline of SPS commences with the groundbreaking
works by Gatos et al., who reported diffusion length of minority carriers in bulk
CdS and GaAs samples by using sub-bandgap illumination during early 1970s [15].
In the next couple of decades, the SPS was applied successfully to a variety of
semiconducting materials by various researchers [16–21]. In early 80 s, the SPS was
also employed to study the effect of different ambience on SPV and to determine the
density of surface states in amorphous materials [22, 23]. Starting in the mid-1990s,
the technique got a revival, triggered mainly by its capability to probe absorption
related phenomena in multiple quantum wells (QWs), quantum dots and various other
nanostructures [24–31]. The SPS has been extensively applied by Shaphira’s group
and subsequently Pollak’s group to carry out quantitative investigations of a variety
of semiconductor interfaces and heterostructures, [32–35] including actual device
structures. [36–38]. The SPS has also been used and found to be very effective
for study epitaxial layers at wafer scales. Huang et al. [38] have applied SPS for
the characterization of vertical cavity surface emitting lasers. Lagowski et al. [39]
employed the SPS for determining minority carrier diffusion length as well as heavy
metal contamination of silicon wafers during the fabrication of ICs. A very detailed
review of these applications has been reported in 2001 by Kronik and Shapira [10].
The SPS is generally performed either by means of Kelvin probe or in the metalinsulator-semiconductor (MIS) configuration. Over these seven decades, however,
the technique has evolved significantly in terms of both the performance of experimental tools as well as the methods for data analysis. Also, the MIS configuration
has become more popular lately due to some advantages [9], and is extensively used
lately [2–6, 40]. The chapter presented here is intended to provide an overview of the
state of the arts in SPS. Subsequently the theoretical framework necessary to understand the physics of surface, interface and the SPS is described, mostly in intuitive
and qualitative way. Following the theoretical framework, the experimental setup for
the SPS has been described in detail along with quite a few variants of measurements,
A. Jariwala et al.
1 Introduction
The surface photovoltage spectroscopy (SPS) relies on the measurements of surface
photovoltage (SPV) phenomenon as a function of incident photon energy. It is a versatile, contactless, non-destructive characterization technique, which has been successfully employed extensively for characterization of various semiconductor materials
and devices. These include surfaces, thin films, bulk materials and nanostructures of
a variety of semiconductors materials and interfaces [1–6].
In early pioneering work, surface photovoltage (SPV) was used to study effects of
adsorbates on the surface potential (Vs) of Ge by Brattain and Bardeen in 1953 [7] and
subsequently by E. O. Johnson in 1957 [8]. Since then it has been used extensively
in the last seven decades in order to probe electronic and optical properties, such as
optical band gap, surface states, surface oxide thickness, minority carrier diffusion
length and their lifetimes for various materials systems. The SPS has also been
applied in case of quantum structures to determine the band-offsets [9–14]. The
major breakthrough in the timeline of SPS commences with the groundbreaking
works by Gatos et al., who reported diffusion length of minority carriers in bulk
CdS and GaAs samples by using sub-bandgap illumination during early 1970s [15].
In the next couple of decades, the SPS was applied successfully to a variety of
semiconducting materials by various researchers [16–21]. In early 80 s, the SPS was
also employed to study the effect of different ambience on SPV and to determine the
density of surface states in amorphous materials [22, 23]. Starting in the mid-1990s,
the technique got a revival, triggered mainly by its capability to probe absorption
related phenomena in multiple quantum wells (QWs), quantum dots and various other
nanostructures [24–31]. The SPS has been extensively applied by Shaphira’s group
and subsequently Pollak’s group to carry out quantitative investigations of a variety
of semiconductor interfaces and heterostructures, [32–35] including actual device
structures. [36–38]. The SPS has also been used and found to be very effective
for study epitaxial layers at wafer scales. Huang et al. [38] have applied SPS for
the characterization of vertical cavity surface emitting lasers. Lagowski et al. [39]
employed the SPS for determining minority carrier diffusion length as well as heavy
metal contamination of silicon wafers during the fabrication of ICs. A very detailed
review of these applications has been reported in 2001 by Kronik and Shapira [10].
The SPS is generally performed either by means of Kelvin probe or in the metalinsulator-semiconductor (MIS) configuration. Over these seven decades, however,
the technique has evolved significantly in terms of both the performance of experimental tools as well as the methods for data analysis. Also, the MIS configuration
has become more popular lately due to some advantages [9], and is extensively used
lately [2–6, 40]. The chapter presented here is intended to provide an overview of the
state of the arts in SPS. Subsequently the theoretical framework necessary to understand the physics of surface, interface and the SPS is described, mostly in intuitive
and qualitative way. Following the theoretical framework, the experimental setup for
the SPS has been described in detail along with quite a few variants of measurements,