As PV capacity in urban areas keeps increasing, non-uniform
illumination of panels will become more prevalent. This could cause the partial
shading to become more frequent, reducing PV system performance. Some ways to
solve this problem is by the use of module-level maximum power point tracking (MPPT),
micro inverters, or reconfigurable modules. To this end, the integration of
metal-oxidesemiconductor field-effect transistor (MOSFET) on solar cells could
play an important role in future methods to prevent this issue. This
integration of a MOSFET allows for module level, and potentially sub-module
level, MPPT, as well as the application of reconfigurable modules to circumvent
this issue. This thesis aims to optimize the MOSFET dimensions and fabrication
process to be able to handle the short circuit current and open circuit voltage
of a PV module, and to analyze the optoelectrical effects under direct
illumination of the MOSFET performance. In this thesis report, a flowchart is
proposed on how to fabricate a working power MOSFET while combining the
fabrication techniques used in the Integrated Circuits and Photovoltaics
industries. This process closely resembles the fabrication of solar cells and
uses similar techniques used to fabricate interdigitated back contacted (IBC)
solar cells. It is shown that It is shown that the use of wider devices can
reduce channel resistance from 167Ω for a PMOS device with a width of 500𝜇m
down to 20Ω for a device with a width of 5000𝜇m. For NMOS devices a similar
relationship can be seen where the channel resistance is 49Ω for a width of 500𝜇m
and 8.1Ω for a device width of 5000𝜇m. The current density of
the devices drop from 115𝜇𝐴/𝜇𝑚
for an NMOS device with a width of 500𝜇m to less than 80𝜇𝐴/𝜇𝑚
for a 5000𝜇m wide device. For PMOS this density drop is
smaller where the drop is from 33𝜇𝐴/𝜇𝑚
to 27𝜇𝐴/𝜇𝑚.
A study on the effects of implantation energy and scattering layer thicknesses
showed that both lower energies and thicker layers yield higher drain currents
and lower channel resistance. A possible explanation for this is that a shift
in the threshold voltage increased the overdrive voltage and therefore the
drain current. In the investigation of the effects of direct illumination on
the electrical characteristics of the device it was found that the threshold
voltage increases for PMOS devices from -0.21V under no illumination to -0.06V
under full spectrum illumination at 1000𝑊/𝑚2 and
decreases for NMOS devices from 0.06V under no illumination to -0.15V under
full spectrum illumination at 1000𝑊/𝑚2.
Furthermore the off state gate leakage current increases by factor 33 under
illumination at 1000𝑊/𝑚2 for NMOS devices and by
a factor of 107 for PMOS devices. The electron mobility of the NMOS transistor
increases with incident light, improving the drain current gate voltage
relationship. The channel resistance for the NMOS devices improved between
5-13%, depending on the intensity of the illumination, while the channel
resistance of the PMOS increases up to 2%.A similar effect for the hole
mobility of the PMOS was not observed. Similarly, the channel resistance of the
NMOS transistor improved, possibly due to the shift in threshold voltage or
improved electron mobility. This improvement in performance was not recognized
for PMOS transistors, however. A flowchart has been proposed for a process in
which a MOSFET is fabricated on the backside of an Interdigitated Back
Contacted (IBC) solar cell while combining as many steps as possible from their
respective flowcharts to reduce complexity and costs, possibly leading the best
balance between MOSFET and IBC fabrication.As PV capacity in urban areas keeps
increasing, non-uniform illumination of panels will become more prevalent. This
could cause the partial shading to become more frequent, reducing PV system
performance. Some ways to solve this problem is by the use of module-level
maximum power point tracking (MPPT), micro inverters, or reconfigurable
modules. To this end, the integration of metal-oxidesemiconductor field-effect
transistor (MOSFET) on solar cells could play an important role in future methods
to prevent this issue. This integration of a MOSFET allows for module level,
and potentially sub-module level, MPPT, as well as the application of
reconfigurable modules to circumvent this issue. This thesis aims to optimize
the MOSFET dimensions and fabrication process to be able to handle the short
circuit current and open circuit voltage of a PV module, and to analyze the
optoelectrical effects under direct illumination of the MOSFET performance. In
this thesis report, a flowchart is proposed on how to fabricate a working power
MOSFET while combining the fabrication techniques used in the Integrated
Circuits and Photovoltaics industries. This process closely resembles the
fabrication of solar cells and uses similar techniques used to fabricate interdigitated
back contacted (IBC) solar cells. It is shown that It is shown that the use of
wider devices can reduce channel resistance from 167Ω for a PMOS device with a
width of 500𝜇m down to 20Ω for a device with a width of 5000𝜇m.
For NMOS devices a similar relationship can be seen where the channel
resistance is 49Ω for a width of 500𝜇m and 8.1Ω for a device
width of 5000𝜇m. The current density of the devices drop from
115𝜇𝐴/𝜇𝑚
for an NMOS device with a width of 500𝜇m to less than 80𝜇𝐴/𝜇𝑚
for a 5000𝜇m wide device. For PMOS this density drop is
smaller where the drop is from 33𝜇𝐴/𝜇𝑚
to 27𝜇𝐴/𝜇𝑚.
A study on the effects of implantation energy and scattering layer thicknesses
showed that both lower energies and thicker layers yield higher drain currents
and lower channel resistance. A possible explanation for this is that a shift
in the threshold voltage increased the overdrive voltage and therefore the
drain current. In the investigation of the effects of direct illumination on
the electrical characteristics of the device it was found that the threshold
voltage increases for PMOS devices from -0.21V under no illumination to -0.06V
under full spectrum illumination at 1000𝑊/𝑚2 and
decreases for NMOS devices from 0.06V under no illumination to -0.15V under
full spectrum illumination at 1000𝑊/𝑚2.
Furthermore the off state gate leakage current increases by factor 33 under
illumination at 1000𝑊/𝑚2 for NMOS devices and by
a factor of 107 for PMOS devices. The electron mobility of the NMOS transistor
increases with incident light, improving the drain current gate voltage
relationship. The channel resistance for the NMOS devices improved between
5-13%, depending on the intensity of the illumination, while the channel
resistance of the PMOS increases up to 2%.A similar effect for the hole
mobility of the PMOS was not observed. Similarly, the channel resistance of the
NMOS transistor improved, possibly due to the shift in threshold voltage or
improved electron mobility. This improvement in performance was not recognized
for PMOS transistors, however. A flowchart has been proposed for a process in
which a MOSFET is fabricated on the backside of an Interdigitated Back
Contacted (IBC) solar cell while combining as many steps as possible from their
respective flowcharts to reduce complexity and costs, possibly leading the best
balance between MOSFET and IBC fabrication. As PV capacity in urban areaskeeps
increasing, non-uniform illumination of panels will become more prevalent.This
could cause the partial shading to become more frequent, reducing PVsystem
performance. Some ways to solve this problem is by the use ofmodule-level
maximum power point tracking (MPPT), micro inverters, orreconfigurable modules.
To this end, the integration ofmetal-oxidesemiconductor field-effect transistor
(MOSFET) on solar cells couldplay an important role in future methods to
prevent this issue. Thisintegration of a MOSFET allows for module level, and
potentially sub-modulelevel, MPPT, as well as the application of reconfigurable
modules to circumventthis issue. This thesis aims to optimize the MOSFET
dimensions and fabricationprocess to be able to handle the short circuit
current and open circuit voltageof a PV module, and to analyze the
optoelectrical effects under directillumination of the MOSFET performance. In
this thesis report, a flowchart isproposed on how to fabricate a working power
MOSFET while combining thefabrication techniques used in the Integrated
Circuits and Photovoltaicsindustries. This process closely resembles the
fabrication of solar cells anduses similar techniques used to fabricate
interdigitated back contacted (IBC)solar cells. It is shown that It is shown
that the use of wider devices canreduce channel resistance from 167Ω for a PMOS
device with a width of 500𝜇m down to 20Ω for a devicewith
a width of 5000𝜇m.For NMOS devices a similar relationship can
be seen where the channelresistance is 49Ω for a width of 500𝜇mand
8.1Ω for a device width of 5000𝜇m.The current density of
the devices drop from 115𝜇𝐴/𝜇𝑚
for an NMOSdevice with a width of 500𝜇mto less than 80𝜇𝐴/𝜇𝑚
for a 5000𝜇m wide device. For PMOSthis density drop is
smaller where the drop is from 33𝜇𝐴/𝜇𝑚
to 27𝜇𝐴/𝜇𝑚.
A study on theeffects of implantation energy and scattering layer thicknesses
showed thatboth lower energies and thicker layers yield higher drain currents
and lowerchannel resistance. A possible explanation for this is that a shift in
thethreshold voltage increased the overdrive voltage and therefore the
draincurrent. In the investigation of the effects of direct illumination on
theelectrical characteristics of the device it was found that the
thresholdvoltage increases for PMOS devices from -0.21V under no illumination
to -0.06Vunder full spectrum illumination at 1000𝑊/𝑚2 and
decreases for NMOSdevices from 0.06V under no illumination to -0.15V under full
spectrumillumination at 1000𝑊/𝑚2.
Furthermore the off stategate leakage current increases by factor 33 under
illumination at 1000𝑊/𝑚2 for NMOS devices and bya
factor of 107 for PMOS devices. The electron mobility of the NMOS
transistorincreases with incident light, improving the drain current gate
voltagerelationship. The channel resistance for the NMOS devices improved
between5-13%, depending on the intensity of the illumination, while the
channelresistance of the PMOS increases up to 2%.A similar effect for the hole
mobilityof the PMOS was not observed. Similarly, the channel resistance of the
NMOStransistor improved, possibly due to the shift in threshold voltage or
improvedelectron mobility. This improvement in performance was not recognized
for PMOStransistors, however. A flowchart has been proposed for a process in
which aMOSFET is fabricated on the backside of an Interdigitated Back Contacted
(IBC)solar cell while combining as many steps as possible from their
respectiveflowcharts to reduce complexity and costs, possibly leading the best
balancebetween MOSFET and IBC fabrication.