Kauth J (2022)
Publication Language: English
Publication Type: Thesis
Publication year: 2022
In order to understand and improve the performance characteristics of high power devices,
the underlying semiconductor physics must be analyzed. An important contribution
to the performance of devices is the hole concentration in aluminium implanted silicon
carbide, which is a prime candidate for high power applications. Previous works have determined
the ionization and compensation ratio of aluminium dopants in silicon carbide.
A second acceptor level has been suggested to account for defects introduced during ion
implantation.
In this work, the charge carrier concentration of aluminium implanted silicon carbide
is measured and the concentrations and ionization energies of two acceptor defects are
determined. The prepared samples were manufactured in a 4H-SiC JFET technology and
implanted with a concentration of 7.5×1016 cm−3 of aluminium and annealed at 1700 °C
for 30 min. The samples are characterized in terms of their sheet resistance, Hall mobility
and charge carrier concentration in the temperature range from 220K to 550K.
For the Hall mobility, the range of values was determined to be between 107 cm2 V−1 s−1
at 220K and 15 cm2 V−1 s−1 at 550K and found to be in agreement with values found in
literature. The sheet resistance determined from test structures is compared with performance
characteristics of devices manufactured with identical implantation profiles. The
two values are found to correlate well with each other.
Determination of the compensation ratio as presented in literature was reproduced,
but found to contain a flaw. For the limited temperature range of the data available for
this work, impossible results for dopant and compensation concentration were produced
by the method. An independent determination of doping concentration and compensation
concentration with the available data was proven to be impossible. Because of the
limitation of the fitting model, a new form of the neutrality equation without variable
compensation concentration is proposed to better fit the experimental data of aluminium
implanted silicon carbide. A fixed value for the compensation is nevertheless taken into
account, recognizing the influence of compensating dopants and defects. Due to a lack
of alternative methods to determine the concentration of compensating defects a concentration
of 0 cm−3 was assumed. The compensating defects due to nitrogen doping of the
epitaxial layer were considered with a total concentration of 7.5 × 1015 cm−3. With the
new form of the neutrality equation, the ionization energies of two acceptor like impurities
were determined to be between 201 meV to 256 meV and 403 meV to 444 meV, comparable
to values found in literature.
The results of this work support the adoption of a second acceptor level, in order
to correctly model aluminium implanted silicon carbide. The need for a wide temperature
range when measuring the charge carrier concentration, in order to determine the
concentration of compensating defects, is shown.
APA:
Kauth, J. (2022). Kompensationseffekt von implantierten Aluminiumdopanden in 4H-SiC (Master thesis).
MLA:
Kauth, Julian. Kompensationseffekt von implantierten Aluminiumdopanden in 4H-SiC. Master thesis, 2022.
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